21631018 has 8 divisors (see below), whose sum is σ = 32558148. Its totient is φ = 10778304.

The previous prime is 21631007. The next prime is 21631033. The reversal of 21631018 is 81013612.

It can be written as a sum of positive squares in 2 ways, for example, as 14085009 + 7546009 = 3753^2 + 2747^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21631018.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17871 + ... + 19042.

Almost surely, 2^21631018 is an apocalyptic number.

21631018 is a deficient number, since it is larger than the sum of its proper divisors (10927130).

21631018 is a wasteful number, since it uses less digits than its factorization.

21631018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37208.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 21631018 is about 4650.9158237921. The cubic root of 21631018 is about 278.6285744070.

The spelling of 21631018 in words is "twenty-one million, six hundred thirty-one thousand, eighteen".