21515013640 has 32 divisors (see below), whose sum is σ = 48426099480. Its totient is φ = 8602926592.

The previous prime is 21515013623. The next prime is 21515013677. The reversal of 21515013640 is 4631051512.

It can be written as a sum of positive squares in 4 ways, for example, as 4329376804 + 17185636836 = 65798^2 + 131094^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21515013599 and 21515013608.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18684 + ... + 208276.

Almost surely, 2^21515013640 is an apocalyptic number.

21515013640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21515013640 is an abundant number, since it is smaller than the sum of its proper divisors (26911085840).

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

21515013640 is a wasteful number, since it uses less digits than its factorization.

21515013640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 192441 (or 192437 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 28.

The spelling of 21515013640 in words is "twenty-one billion, five hundred fifteen million, thirteen thousand, six hundred forty".