21912816 has 20 divisors (see below), whose sum is σ = 56608232. Its totient is φ = 7304256.

The previous prime is 21912799. The next prime is 21912823. The reversal of 21912816 is 61821912.

It is a happy number.

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, 228211 + ... + 228306.

Almost surely, 2^21912816 is an apocalyptic number.

It is an amenable number.

21912816 is an abundant number, since it is smaller than the sum of its proper divisors (34695416).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21912816 is a wasteful number, since it uses less digits than its factorization.

21912816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 456528 (or 456522 counting only the distinct ones).

The product of its digits is 1728, while the sum is 30.

The square root of 21912816 is about 4681.1126882398. The cubic root of 21912816 is about 279.8333021367.

The spelling of 21912816 in words is "twenty-one million, nine hundred twelve thousand, eight hundred sixteen".