21170655657 has 12 divisors (see below), whose sum is σ = 30966923520. Its totient is φ = 13935114648.

The previous prime is 21170655643. The next prime is 21170655673. The reversal of 21170655657 is 75655607112.

21170655657 is a `hidden beast` number, since 2 + 11 + 70 + 6 + 5 + 565 + 7 = 666.

It is not a de Polignac number, because 21170655657 - 2²⁸ = 20902220201 is a prime.

It is a super-2 number, since 2×21170655657² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21170655617) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14887233 + ... + 14888654.

It is an arithmetic number, because the mean of its divisors is an integer number (2580576960).

Almost surely, 2^21170655657 is an apocalyptic number.

It is an amenable number.

21170655657 is a deficient number, since it is larger than the sum of its proper divisors (9796267863).

21170655657 is a wasteful number, since it uses less digits than its factorization.

21170655657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29775972 (or 29775969 counting only the distinct ones).

The product of its (nonzero) digits is 441000, while the sum is 45.

The spelling of 21170655657 in words is "twenty-one billion, one hundred seventy million, six hundred fifty-five thousand, six hundred fifty-seven".