21681945572 has 12 divisors (see below), whose sum is σ = 43363891200. Its totient is φ = 9292262376.

The previous prime is 21681945563. The next prime is 21681945611. The reversal of 21681945572 is 27554918612.

21681945572 is an admirable number.

It is a self number, because there is not a number n which added to its sum of digits gives 21681945572.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 387177572 + ... + 387177627.

It is an arithmetic number, because the mean of its divisors is an integer number (3613657600).

Almost surely, 2^21681945572 is an apocalyptic number.

It is an amenable number.

21681945572 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21681945572 is a wasteful number, since it uses less digits than its factorization.

21681945572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 774355210 (or 774355208 counting only the distinct ones).

The product of its digits is 1209600, while the sum is 50.

The spelling of 21681945572 in words is "twenty-one billion, six hundred eighty-one million, nine hundred forty-five thousand, five hundred seventy-two".