31731518218 has 4 divisors (see below), whose sum is σ = 47597277330. Its totient is φ = 15865759108.

The previous prime is 31731518201. The next prime is 31731518227. The reversal of 31731518218 is 81281513713.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 28061945289 + 3669572929 = 167517^2 + 60577^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7932879553 + ... + 7932879556.

Almost surely, 2^31731518218 is an apocalyptic number.

31731518218 is a deficient number, since it is larger than the sum of its proper divisors (15865759112).

31731518218 is a wasteful number, since it uses less digits than its factorization.

31731518218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15865759111.

The product of its digits is 40320, while the sum is 40.

It can be divided in two parts, 317315 and 18218, that added together give a palindrome (335533).

The spelling of 31731518218 in words is "thirty-one billion, seven hundred thirty-one million, five hundred eighteen thousand, two hundred eighteen".