21916161 has 12 divisors (see below), whose sum is σ = 32013540. Its totient is φ = 14446080.

The previous prime is 21916157. The next prime is 21916187. The reversal of 21916161 is 16161912.

It can be written as a sum of positive squares in 2 ways, for example, as 8520561 + 13395600 = 2919^2 + 3660^2 .

It is not a de Polignac number, because 21916161 - 2² = 21916157 is a prime.

It is a super-2 number, since 2×21916161² = 960636225955842, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21916151) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12880 + ... + 14481.

It is an arithmetic number, because the mean of its divisors is an integer number (2667795).

Almost surely, 2^21916161 is an apocalyptic number.

It is an amenable number.

21916161 is a deficient number, since it is larger than the sum of its proper divisors (10097379).

21916161 is a wasteful number, since it uses less digits than its factorization.

21916161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27456 (or 27453 counting only the distinct ones).

The product of its digits is 648, while the sum is 27.

The square root of 21916161 is about 4681.4699614544. The cubic root of 21916161 is about 279.8475403002.

The spelling of 21916161 in words is "twenty-one million, nine hundred sixteen thousand, one hundred sixty-one".