20991216 has 40 divisors (see below), whose sum is σ = 55980544. Its totient is φ = 6770880.

The previous prime is 20991211. The next prime is 20991227. The reversal of 20991216 is 61219902.

It is a happy number.

It is a super-2 number, since 2×20991216² = 881262298317312, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20991211) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5566 + ... + 8541.

Almost surely, 2^20991216 is an apocalyptic number.

It is an amenable number.

20991216 is an abundant number, since it is smaller than the sum of its proper divisors (34989328).

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

20991216 is a wasteful number, since it uses less digits than its factorization.

20991216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14149 (or 14143 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 20991216 is about 4581.6171817383. The cubic root of 20991216 is about 275.8539449878.

The spelling of 20991216 in words is "twenty million, nine hundred ninety-one thousand, two hundred sixteen".