18218531 has 8 divisors (see below), whose sum is σ = 18493440. Its totient is φ = 17945928.

The previous prime is 18218527. The next prime is 18218561. The reversal of 18218531 is 13581281.

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

It is a cyclic number.

It is not a de Polignac number, because 18218531 - 2² = 18218527 is a prime.

It is a super-2 number, since 2×18218531² = 663829743595922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18218494 and 18218503.

It is not an unprimeable number, because it can be changed into a prime (18218561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20780 + ... + 21638.

It is an arithmetic number, because the mean of its divisors is an integer number (2311680).

Almost surely, 2^18218531 is an apocalyptic number.

18218531 is a deficient number, since it is larger than the sum of its proper divisors (274909).

18218531 is a wasteful number, since it uses less digits than its factorization.

18218531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1153.

The product of its digits is 1920, while the sum is 29.

The square root of 18218531 is about 4268.3171156792. The cubic root of 18218531 is about 263.1304561771.

The spelling of 18218531 in words is "eighteen million, two hundred eighteen thousand, five hundred thirty-one".