21117138 has 64 divisors (see below), whose sum is σ = 50995200. Its totient is φ = 5821200.

The previous prime is 21117137. The next prime is 21117193. The reversal of 21117138 is 83171112.

It is a happy number.

It is a super-2 number, since 2×21117138² = 891867034622088, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21117137) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 63633 + ... + 63963.

It is an arithmetic number, because the mean of its divisors is an integer number (796800).

Almost surely, 2^21117138 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21117138, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25497600).

21117138 is an abundant number, since it is smaller than the sum of its proper divisors (29878062).

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

21117138 is a wasteful number, since it uses less digits than its factorization.

21117138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388 (or 374 counting only the distinct ones).

The product of its digits is 336, while the sum is 24.

The square root of 21117138 is about 4595.3387252737. The cubic root of 21117138 is about 276.4044427581.

The spelling of 21117138 in words is "twenty-one million, one hundred seventeen thousand, one hundred thirty-eight".