20556621666 has 64 divisors (see below), whose sum is σ = 52242278400. Its totient is φ = 5869384848.

The previous prime is 20556621623. The next prime is 20556621689. The reversal of 20556621666 is 66612665502.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 571861 + ... + 606743.

It is an arithmetic number, because the mean of its divisors is an integer number (816285600).

Almost surely, 2^20556621666 is an apocalyptic number.

20556621666 is an abundant number, since it is smaller than the sum of its proper divisors (31685656734).

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

20556621666 is a wasteful number, since it uses less digits than its factorization.

20556621666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36460 (or 36454 counting only the distinct ones).

The product of its (nonzero) digits is 777600, while the sum is 45.

The spelling of 20556621666 in words is "twenty billion, five hundred fifty-six million, six hundred twenty-one thousand, six hundred sixty-six".