21591951364 has 9 divisors (see below), whose sum is σ = 37786429191. Its totient is φ = 10795828740.

The previous prime is 21591951347. The next prime is 21591951371. The reversal of 21591951364 is 46315919512.

It is a happy number.

The square root of 21591951364 is 146942.

It is a perfect power (a square), and thus also a powerful number.

It is a Duffinian number.

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 in 2 ways as a sum of consecutive naturals, for example, 257149 + ... + 330619.

Almost surely, 2^21591951364 is an apocalyptic number.

21591951364 is the 146942-nd square number.

It is an amenable number.

21591951364 is a deficient number, since it is larger than the sum of its proper divisors (16194477827).

21591951364 is an frugal number, since it uses more digits than its factorization.

21591951364 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146946 (or 73473 counting only the distinct ones).

The product of its digits is 291600, while the sum is 46.

The spelling of 21591951364 in words is "twenty-one billion, five hundred ninety-one million, nine hundred fifty-one thousand, three hundred sixty-four".