21218318 has 12 divisors (see below), whose sum is σ = 34984320. Its totient is φ = 9644580.

The previous prime is 21218317. The next prime is 21218321. The reversal of 21218318 is 81381212.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218311) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 43598 + ... + 44081.

It is an arithmetic number, because the mean of its divisors is an integer number (2915360).

Almost surely, 2^21218318 is an apocalyptic number.

21218318 is a deficient number, since it is larger than the sum of its proper divisors (13766002).

21218318 is a wasteful number, since it uses less digits than its factorization.

21218318 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87703 (or 87692 counting only the distinct ones).

The product of its digits is 768, while the sum is 26.

The square root of 21218318 is about 4606.3345514628. The cubic root of 21218318 is about 276.8451914671.

The spelling of 21218318 in words is "twenty-one million, two hundred eighteen thousand, three hundred eighteen".