21606605660 has 24 divisors (see below), whose sum is σ = 45790150560. Its totient is φ = 8563351104.

The previous prime is 21606605653. The next prime is 21606605681. The reversal of 21606605660 is 6650660612.

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, 4953464 + ... + 4957823.

It is an arithmetic number, because the mean of its divisors is an integer number (1907922940).

Almost surely, 2^21606605660 is an apocalyptic number.

21606605660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21606605660 is an abundant number, since it is smaller than the sum of its proper divisors (24183544900).

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

21606605660 is a wasteful number, since it uses less digits than its factorization.

21606605660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9911405 (or 9911403 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 38.

The spelling of 21606605660 in words is "twenty-one billion, six hundred six million, six hundred five thousand, six hundred sixty".