9999998

9999998 is the natural number following 9999997 and preceding 9999999. It is an even number, meaning it is divisible by 2, and it is not a prime number, as it has more than two distinct positive divisors: 1, 2, 4999999, and 9999998 itself. The sum of its digits is 57, which is divisible by 9, making 9999998 a Harshad number.

In the binary numeral system, 9999998 is represented as 11101110011011011011110, consisting of 27 ones and 10 zeros. It is also a repunit, a number consisting of repeated digits, in this case, the digit 9.

9999998 is the eighth power of 3, calculated as 3^8. It is also a perfect totient number, meaning that Euler's totient function φ(n) equals n-1 for this number. The totient function counts the positive integers up to a given integer n that are relatively prime to n.

In the context of the Fibonacci sequence, 9999998 is not a Fibonacci number, as it does not appear in the sequence. However, it is a Lucas number, the 16th in the sequence, calculated as L(16).

9999998 is also notable in the field of cryptography, as it is a safe prime, a prime number of the form 2p+1, where p is also a prime number. This property makes it suitable for use in certain types of cryptographic systems.