21615639220 has 24 divisors (see below), whose sum is σ = 51877534464. Its totient is φ = 7411076256.

The previous prime is 21615639217. The next prime is 21615639263. The reversal of 21615639220 is 2293651612.

It is a self number, because there is not a number n which added to its sum of digits gives 21615639220.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77198572 + ... + 77198851.

It is an arithmetic number, because the mean of its divisors is an integer number (2161563936).

Almost surely, 2^21615639220 is an apocalyptic number.

21615639220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21615639220 is an abundant number, since it is smaller than the sum of its proper divisors (30261895244).

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

21615639220 is a wasteful number, since it uses less digits than its factorization.

21615639220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154397439 (or 154397437 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 37.

The spelling of 21615639220 in words is "twenty-one billion, six hundred fifteen million, six hundred thirty-nine thousand, two hundred twenty".