21918138 has 32 divisors (see below), whose sum is σ = 48019392. Its totient is φ = 6614400.

The previous prime is 21918131. The next prime is 21918139. The reversal of 21918138 is 83181912.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a junction number, because it is equal to n+sod(n) for n = 21918099 and 21918108.

It is not an unprimeable number, because it can be changed into a prime (21918131) 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, 20128 + ... + 21188.

It is an arithmetic number, because the mean of its divisors is an integer number (1500606).

Almost surely, 2^21918138 is an apocalyptic number.

21918138 is an abundant number, since it is smaller than the sum of its proper divisors (26101254).

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

21918138 is a wasteful number, since it uses less digits than its factorization.

21918138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1390.

The product of its digits is 3456, while the sum is 33.

The square root of 21918138 is about 4681.6811083200. The cubic root of 21918138 is about 279.8559548207.

The spelling of 21918138 in words is "twenty-one million, nine hundred eighteen thousand, one hundred thirty-eight".