17564426921 has 2 divisors, whose sum is σ = 17564426922. Its totient is φ = 17564426920.

The previous prime is 17564426827. The next prime is 17564426923. The reversal of 17564426921 is 12962446571.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15179472025 + 2384954896 = 123205^2 + 48836^2 .

It is a cyclic number.

It is not a de Polignac number, because 17564426921 - 2²² = 17560232617 is a prime.

Together with 17564426923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (17564426923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8782213460 + 8782213461.

It is an arithmetic number, because the mean of its divisors is an integer number (8782213461).

Almost surely, 2^17564426921 is an apocalyptic number.

It is an amenable number.

17564426921 is a deficient number, since it is larger than the sum of its proper divisors (1).

17564426921 is an equidigital number, since it uses as much as digits as its factorization.

17564426921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 725760, while the sum is 47.

The spelling of 17564426921 in words is "seventeen billion, five hundred sixty-four million, four hundred twenty-six thousand, nine hundred twenty-one".