21993812 has 24 divisors (see below), whose sum is σ = 39961152. Its totient is φ = 10584000.

The previous prime is 21993809. The next prime is 21993823. The reversal of 21993812 is 21839912.

It is a congruent 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 7 ways as a sum of consecutive naturals, for example, 11312 + ... + 13112.

It is an arithmetic number, because the mean of its divisors is an integer number (1665048).

Almost surely, 2^21993812 is an apocalyptic number.

It is an amenable number.

21993812 is a deficient number, since it is larger than the sum of its proper divisors (17967340).

21993812 is a wasteful number, since it uses less digits than its factorization.

21993812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1919 (or 1917 counting only the distinct ones).

The product of its digits is 7776, while the sum is 35.

The square root of 21993812 is about 4689.7560704156. The cubic root of 21993812 is about 280.1776593605.

The spelling of 21993812 in words is "twenty-one million, nine hundred ninety-three thousand, eight hundred twelve".