21117565401 has 4 divisors (see below), whose sum is σ = 28156753872. Its totient is φ = 14078376932.

The previous prime is 21117565379. The next prime is 21117565433. The reversal of 21117565401 is 10456571112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21117565401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21117565471) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3519594231 + ... + 3519594236.

It is an arithmetic number, because the mean of its divisors is an integer number (7039188468).

Almost surely, 2^21117565401 is an apocalyptic number.

It is an amenable number.

21117565401 is a deficient number, since it is larger than the sum of its proper divisors (7039188471).

21117565401 is an equidigital number, since it uses as much as digits as its factorization.

21117565401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7039188470.

The product of its (nonzero) digits is 8400, while the sum is 33.

The spelling of 21117565401 in words is "twenty-one billion, one hundred seventeen million, five hundred sixty-five thousand, four hundred one".