21668667660 has 72 divisors (see below), whose sum is σ = 66805838736. Its totient is φ = 5683582080.

The previous prime is 21668667659. The next prime is 21668667703. The reversal of 21668667660 is 6676686612.

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21668667597 and 21668667606.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 975754 + ... + 997713.

Almost surely, 2^21668667660 is an apocalyptic number.

21668667660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21668667660 is an abundant number, since it is smaller than the sum of its proper divisors (45137171076).

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

21668667660 is a wasteful number, since it uses less digits than its factorization.

21668667660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1973543 (or 1973538 counting only the distinct ones).

The product of its (nonzero) digits is 5225472, while the sum is 54.

The spelling of 21668667660 in words is "twenty-one billion, six hundred sixty-eight million, six hundred sixty-seven thousand, six hundred sixty".