21197637864 has 48 divisors (see below), whose sum is σ = 61826446500. Its totient is φ = 6522349824.

The previous prime is 21197637863. The next prime is 21197637871. The reversal of 21197637864 is 46873679112.

21197637864 is a `hidden beast` number, since 21 + 197 + 6 + 378 + 64 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 16233308100 + 4964329764 = 127410^2 + 70458^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21197637864.

It is not an unprimeable number, because it can be changed into a prime (21197637863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11322589 + ... + 11324460.

Almost surely, 2^21197637864 is an apocalyptic number.

21197637864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21197637864 is an abundant number, since it is smaller than the sum of its proper divisors (40628808636).

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

21197637864 is a wasteful number, since it uses less digits than its factorization.

21197637864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22647074 (or 22647067 counting only the distinct ones).

The product of its digits is 3048192, while the sum is 54.

The spelling of 21197637864 in words is "twenty-one billion, one hundred ninety-seven million, six hundred thirty-seven thousand, eight hundred sixty-four".