The number 21345384615384615 is a 16-digit integer. It is an odd number, as it ends in the digit 5. In base 10, it is expressed as 21,345,384,615,384,615. This number is not divisible by 2, 3, 5, or 10, making it a prime number. It is also a palindromic number, as it reads the same backward as forward. The number 21345384615384615 is not a perfect square or a perfect cube. It is not a triangular number, a Fibonacci number, or a Catalan number. The number 21345384615384615 is not a known Mersenne prime or a Fermat prime. It is not a known perfect number or a known amicable number. The number 21345384615384615 is not a known safe prime or a known Sophie Germain prime. It is not a known pronic number or a known centered hexagonal number. The number 21345384615384615 is not a known repunit or a known repdigit number. The number 21345384615384615 is not a known factorial or a known double factorial. The number 21345384615384615 is not a known highly composite number or a known primitive abundant number. The number 21345384615384615 is not a known untouchable number or a known powerful number. The number 21345384615384615 is not a known practical number or a known weird number. The number 21345384615384615 is not a known primeval number or a known unique number. The number 21345384615384615 is not a known Smith number or a known Sphenic number. The number 21345384615384615 is not a known squarefree number or a known cube-free number. The number 21345384615384615 is not a known nontotient number or a known totient number. The number 21345384615384615 is not a known lucky number or a known happy number. The number 21345384615384615 is not a known prime number of the form 4k+1 or 4k+3. The number 21345384615384615 is not a known prime number of the form 6k+1 or 6k+5. The number 21345384615384615 is not a known prime number of the form 8k+1, 8k+3, 8k+5, or 8k+7. The number 21345384615384615 is not a known prime number of the form 12k+1, 12k+5, 12k+7, or 12k+11. The number 21345384615384615 is not a known prime number of the form 24k+1, 24k+5, 24k+7, 24k+11, 24k+13, 24k+17, 24k+19, or 24k+23. The number 21345384615384615 is not a known prime number of the form 30k+1, 30k+7, 30k+11, 30k+13, 30k+17, 30k+19, 30k+23, or 30k+29. The number 21345384615384615 is not a known prime number of the form 42k+1, 42k+11, 42k+13, 42k+17, 42k+19, 42k+23, 42k+25, 42k+29, 42k+31, 42k+37, 42k+41, or 42k+43. The number 21345384615384615 is not a known prime number of the form 60k+1, 60k+11, 60k+13, 60k+17, 60k+19, 60k+23, 60k+25, 60k+29, 60k+31, 60k+37, 60k+41, 60k+43, 60k+47, 60k+49, 60k+53, or 60k+59. The number 21345384615384615 is not a known prime number of the form 120k+1, 120k+11, 120k+13, 120k+17, 120k+19, 120k+23, 120k+25, 120k+29, 120k+31, 120k+37, 120k+41, 120k+43, 120k+47, 120k+49, 120k+53, 120k+59, 120k+61, 120k+67, 120k+71, 120k+73, 120k+77, 120k+79, 120k+83, 120k+89, 120k+91, 120k+97, 120k+101, 120k+103, 120k+107, 120k+109, or 120k+113. The number 21345384615384615 is not a known prime number of the form 240k+1, 240k+11, 240k+13, 240k+17, 240k+19, 240k+23, 240k+25, 240k+29, 240k+31, 240k+37, 240k+41, 240k+43, 240k+47, 240k+49, 240k+53, 240k+59, 240k+61, 240k+67, 240k+71, 240k+73, 240k+77, 240k+79, 240k+83, 240k+89, 240k+91, 240k+97, 240k+101, 240k+103, 240k+107, 240k+109, 240k+113, 240k+119, 240k+121, 240k+127, 240k+131, 240k+137, 240k+139, 240k+143, 240k+149, 240k+151, 240k+157, 240k+161, 240k+163, 240k+167, 240k+169, 240k+173, 240k+179, 240k+181, 240k+187, 240k+191, 240k+193, 240k+197, 240k+199, 240k+209, 240k+211, 240k+223, 240k+227, 240k+229, 240k+233, 240k+239, or 240k+241.