21512

21512 is a natural number that follows 21511 and precedes 21513. In base-10 notation it is a palindrome, reading the same forward and backward (2-1-5-1-2).

Prime factorization: 21512 = 2^3 × 2689, where 2689 is a prime number. Therefore the divisors are 1, 2, 4, 8, 2689, 5378, 10756, and 21512. The sum of proper divisors is 18838, which is less than 21512, so 21512 is a deficient number.

In other bases: binary 0101010000001000; hex 0x5408; octal 52010. It is not a palindrome in those bases, but remains a decimal palindrome.

Other properties: the sum of digits is 11, giving a digital root of 2. It is divisible by 2 and by 8, as reflected in its factorization. The Euler totient function yields φ(21512) = 10752. The square root of 21512 is approximately 146.6.

There is no widely recognized special mathematical significance attached to 21512 beyond these properties. As a five-digit decimal palindrome, it is part of the class of numbers that read the same forward and backward in base 10, a characteristic shared by many numbers in this range.