21255205025517 has 32 divisors (see below), whose sum is σ = 29951957713920. Its totient is φ = 13370321790720.

The previous prime is 21255205025501. The next prime is 21255205025533. The reversal of 21255205025517 is 71552050255212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21255205025501) and next prime (21255205025533).

It is not a de Polignac number, because 21255205025517 - 2⁴ = 21255205025501 is a prime.

It is a super-2 number, since 2×21255205025517² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255205225517) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 68218518 + ... + 68529384.

It is an arithmetic number, because the mean of its divisors is an integer number (935998678560).

Almost surely, 2^{21255205025517} is an apocalyptic number.

It is an amenable number.

21255205025517 is a deficient number, since it is larger than the sum of its proper divisors (8696752688403).

21255205025517 is a wasteful number, since it uses less digits than its factorization.

21255205025517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315713.

The product of its (nonzero) digits is 350000, while the sum is 42.

The spelling of 21255205025517 in words is "twenty-one trillion, two hundred fifty-five billion, two hundred five million, twenty-five thousand, five hundred seventeen".