21809912 has 16 divisors (see below), whose sum is σ = 43299360. Its totient is φ = 10263424.

The previous prime is 21809903. The next prime is 21809923. The reversal of 21809912 is 21990812.

It is a happy number.

It is a super-2 number, since 2×21809912² = 951344522895488, which contains 22 as substring.

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 3 ways as a sum of consecutive naturals, for example, 80048 + ... + 80319.

It is an arithmetic number, because the mean of its divisors is an integer number (2706210).

Almost surely, 2^21809912 is an apocalyptic number.

It is an amenable number.

21809912 is a deficient number, since it is larger than the sum of its proper divisors (21489448).

21809912 is a wasteful number, since it uses less digits than its factorization.

21809912 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160390 (or 160386 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 21809912 is about 4670.1083499208. The cubic root of 21809912 is about 279.3945762332.

The spelling of 21809912 in words is "twenty-one million, eight hundred nine thousand, nine hundred twelve".