21917916 has 18 divisors (see below), whose sum is σ = 55403712. Its totient is φ = 7305960.

The previous prime is 21917891. The next prime is 21917921. The reversal of 21917916 is 61971912.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 608831 = 21917916 / (2 + 1 + 9 + 1 + 7 + 9 + 1 + 6).

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 5 ways as a sum of consecutive naturals, for example, 304380 + ... + 304451.

It is an arithmetic number, because the mean of its divisors is an integer number (3077984).

Almost surely, 2^21917916 is an apocalyptic number.

It is an amenable number.

21917916 is an abundant number, since it is smaller than the sum of its proper divisors (33485796).

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

21917916 is a wasteful number, since it uses less digits than its factorization.

21917916 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 608841 (or 608836 counting only the distinct ones).

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

The square root of 21917916 is about 4681.6573988279. The cubic root of 21917916 is about 279.8550099680.

The spelling of 21917916 in words is "twenty-one million, nine hundred seventeen thousand, nine hundred sixteen".