21721666672 has 10 divisors (see below), whose sum is σ = 42085729208. Its totient is φ = 10860833328.

The previous prime is 21721666639. The next prime is 21721666711. The reversal of 21721666672 is 27666612712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 678802068 + ... + 678802099.

Almost surely, 2^21721666672 is an apocalyptic number.

It is an amenable number.

21721666672 is a deficient number, since it is larger than the sum of its proper divisors (20364062536).

21721666672 is a wasteful number, since it uses less digits than its factorization.

21721666672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1357604175 (or 1357604169 counting only the distinct ones).

The product of its digits is 508032, while the sum is 46.

The spelling of 21721666672 in words is "twenty-one billion, seven hundred twenty-one million, six hundred sixty-six thousand, six hundred seventy-two".