21658216 has 16 divisors (see below), whose sum is σ = 40846500. Its totient is φ = 10765824.

The previous prime is 21658213. The next prime is 21658229. The reversal of 21658216 is 61285612.

It can be written as a sum of positive squares in 2 ways, for example, as 21585316 + 72900 = 4646^2 + 270^2 .

It is not an unprimeable number, because it can be changed into a prime (21658213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6441 + ... + 9208.

Almost surely, 2^21658216 is an apocalyptic number.

It is an amenable number.

21658216 is a deficient number, since it is larger than the sum of its proper divisors (19188284).

21658216 is a wasteful number, since it uses less digits than its factorization.

21658216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15828 (or 15824 counting only the distinct ones).

The product of its digits is 5760, while the sum is 31.

The square root of 21658216 is about 4653.8388455124. The cubic root of 21658216 is about 278.7453044045.

The spelling of 21658216 in words is "twenty-one million, six hundred fifty-eight thousand, two hundred sixteen".