21233663991 has 12 divisors (see below), whose sum is σ = 31040377368. Its totient is φ = 13985223984.

The previous prime is 21233663989. The next prime is 21233664083. The reversal of 21233663991 is 19936633212.

21233663991 is a `hidden beast` number, since 2 + 1 + 2 + 3 + 3 + 6 + 639 + 9 + 1 = 666.

It is not a de Polignac number, because 21233663991 - 2¹ = 21233663989 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21233663791) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14211880 + ... + 14213373.

It is an arithmetic number, because the mean of its divisors is an integer number (2586698114).

Almost surely, 2^21233663991 is an apocalyptic number.

21233663991 is a deficient number, since it is larger than the sum of its proper divisors (9806713377).

21233663991 is a wasteful number, since it uses less digits than its factorization.

21233663991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28425342 (or 28425339 counting only the distinct ones).

The product of its digits is 314928, while the sum is 45.

It can be divided in two parts, 2123366399 and 1, that added together give a square (2123366400 = 46080²).

The spelling of 21233663991 in words is "twenty-one billion, two hundred thirty-three million, six hundred sixty-three thousand, nine hundred ninety-one".