21207956816 has 20 divisors (see below), whose sum is σ = 41585484192. Its totient is φ = 10476218976.

The previous prime is 21207956767. The next prime is 21207956821. The reversal of 21207956816 is 61865970212.

It is a happy number.

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, 7983596 + ... + 7986251.

Almost surely, 2^21207956816 is an apocalyptic number.

It is an amenable number.

21207956816 is a deficient number, since it is larger than the sum of its proper divisors (20377527376).

21207956816 is a wasteful number, since it uses less digits than its factorization.

21207956816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15969938 (or 15969932 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 47.

The spelling of 21207956816 in words is "twenty-one billion, two hundred seven million, nine hundred fifty-six thousand, eight hundred sixteen".