21211138 has 32 divisors (see below), whose sum is σ = 37288944. Its totient is φ = 8957952.

The previous prime is 21211109. The next prime is 21211139. The reversal of 21211138 is 83111212.

It can be written as a sum of positive squares in 8 ways, for example, as 20007729 + 1203409 = 4473^2 + 1097^2 .

It is not an unprimeable number, because it can be changed into a prime (21211139) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15706 + ... + 17002.

Almost surely, 2^21211138 is an apocalyptic number.

21211138 is a deficient number, since it is larger than the sum of its proper divisors (16077806).

21211138 is a wasteful number, since it uses less digits than its factorization.

21211138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1366.

The product of its digits is 96, while the sum is 19.

The square root of 21211138 is about 4605.5551239780. Note that the first 3 decimals coincide. The cubic root of 21211138 is about 276.8139610191.

The spelling of 21211138 in words is "twenty-one million, two hundred eleven thousand, one hundred thirty-eight".