21681382872 has 16 divisors (see below), whose sum is σ = 54203457240. Its totient is φ = 7227127616.

The previous prime is 21681382861. The next prime is 21681382903. The reversal of 21681382872 is 27828318612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 451695453 + ... + 451695500.

Almost surely, 2^21681382872 is an apocalyptic number.

It is an amenable number.

21681382872 is an abundant number, since it is smaller than the sum of its proper divisors (32522074368).

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

21681382872 is a wasteful number, since it uses less digits than its factorization.

21681382872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 903390962 (or 903390958 counting only the distinct ones).

The product of its digits is 516096, while the sum is 48.

The spelling of 21681382872 in words is "twenty-one billion, six hundred eighty-one million, three hundred eighty-two thousand, eight hundred seventy-two".