21507187836 has 24 divisors (see below), whose sum is σ = 50818673920. Its totient is φ = 7078314672.

The previous prime is 21507187787. The next prime is 21507187853. The reversal of 21507187836 is 63878170512.

It is a happy number.

It is a super-2 number, since 2×21507187836² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11342506 + ... + 11344401.

Almost surely, 2^21507187836 is an apocalyptic number.

It is an amenable number.

21507187836 is an abundant number, since it is smaller than the sum of its proper divisors (29311486084).

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

21507187836 is a wasteful number, since it uses less digits than its factorization.

21507187836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22686993 (or 22686991 counting only the distinct ones).

The product of its (nonzero) digits is 564480, while the sum is 48.

The spelling of 21507187836 in words is "twenty-one billion, five hundred seven million, one hundred eighty-seven thousand, eight hundred thirty-six".