21660515220 has 24 divisors (see below), whose sum is σ = 60649442784. Its totient is φ = 5776137376.

The previous prime is 21660515197. The next prime is 21660515237. The reversal of 21660515220 is 2251506612.

It is a Harshad number since it is a multiple of its sum of digits (30).

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, 180504234 + ... + 180504353.

It is an arithmetic number, because the mean of its divisors is an integer number (2527060116).

Almost surely, 2^21660515220 is an apocalyptic number.

21660515220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21660515220 is an abundant number, since it is smaller than the sum of its proper divisors (38988927564).

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

21660515220 is a wasteful number, since it uses less digits than its factorization.

21660515220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 361008599 (or 361008597 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 30.

The spelling of 21660515220 in words is "twenty-one billion, six hundred sixty million, five hundred fifteen thousand, two hundred twenty".