21117007897 has 2 divisors, whose sum is σ = 21117007898. Its totient is φ = 21117007896.

The previous prime is 21117007889. The next prime is 21117007907. The reversal of 21117007897 is 79870071112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16196125696 + 4920882201 = 127264^2 + 70149^2 .

It is a cyclic number.

It is not a de Polignac number, because 21117007897 - 2³ = 21117007889 is a prime.

It is not a weakly prime, because it can be changed into another prime (21117004897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10558503948 + 10558503949.

It is an arithmetic number, because the mean of its divisors is an integer number (10558503949).

Almost surely, 2^21117007897 is an apocalyptic number.

It is an amenable number.

21117007897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21117007897 is an equidigital number, since it uses as much as digits as its factorization.

21117007897 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 49392, while the sum is 43.

The spelling of 21117007897 in words is "twenty-one billion, one hundred seventeen million, seven thousand, eight hundred ninety-seven".