21257193708 has 18 divisors (see below), whose sum is σ = 53733461964. Its totient is φ = 7085731224.

The previous prime is 21257193707. The next prime is 21257193733. The reversal of 21257193708 is 80739175212.

21257193708 is a `hidden beast` number, since 2 + 1 + 2 + 571 + 9 + 3 + 70 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is not an unprimeable number, because it can be changed into a prime (21257193707) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 295238766 + ... + 295238837.

Almost surely, 2^21257193708 is an apocalyptic number.

It is an amenable number.

21257193708 is an abundant number, since it is smaller than the sum of its proper divisors (32476268256).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21257193708 is a wasteful number, since it uses less digits than its factorization.

21257193708 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 590477613 (or 590477608 counting only the distinct ones).

The product of its (nonzero) digits is 211680, while the sum is 45.

The spelling of 21257193708 in words is "twenty-one billion, two hundred fifty-seven million, one hundred ninety-three thousand, seven hundred eight".