21591966208 has 20 divisors (see below), whose sum is σ = 43141761630. Its totient is φ = 10795982848.

The previous prime is 21591966181. The next prime is 21591966229. The reversal of 21591966208 is 80266919512.

It can be written as a sum of positive squares in only one way, i.e., 21587837184 + 4129024 = 146928^2 + 2032^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21085393 + ... + 21086416.

Almost surely, 2^21591966208 is an apocalyptic number.

It is an amenable number.

21591966208 is a deficient number, since it is larger than the sum of its proper divisors (21549795422).

21591966208 is an frugal number, since it uses more digits than its factorization.

21591966208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42171827 (or 42171811 counting only the distinct ones).

The product of its (nonzero) digits is 466560, while the sum is 49.

The spelling of 21591966208 in words is "twenty-one billion, five hundred ninety-one million, nine hundred sixty-six thousand, two hundred eight".