21991716 has 24 divisors (see below), whose sum is σ = 57015840. Its totient is φ = 7330536.

The previous prime is 21991699. The next prime is 21991733. The reversal of 21991716 is 61719912.

It is an interprime number because it is at equal distance from previous prime (21991699) and next prime (21991733).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 101706 + ... + 101921.

It is an arithmetic number, because the mean of its divisors is an integer number (2375660).

Almost surely, 2^21991716 is an apocalyptic number.

It is an amenable number.

21991716 is an abundant number, since it is smaller than the sum of its proper divisors (35024124).

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

21991716 is a wasteful number, since it uses less digits than its factorization.

21991716 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203640 (or 203632 counting only the distinct ones).

The product of its digits is 6804, while the sum is 36.

The square root of 21991716 is about 4689.5325993109. The cubic root of 21991716 is about 280.1687588112.

The spelling of 21991716 in words is "twenty-one million, nine hundred ninety-one thousand, seven hundred sixteen".