31021218 has 40 divisors (see below), whose sum is σ = 70841628. Its totient is φ = 10142496.

The previous prime is 31021171. The next prime is 31021219. The reversal of 31021218 is 81212013.

It can be written as a sum of positive squares in 2 ways, for example, as 28869129 + 2152089 = 5373^2 + 1467^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nialpdrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 31021218.

It is not an unprimeable number, because it can be changed into a prime (31021219) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 6780 + ... + 10392.

Almost surely, 2^31021218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31021218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35420814).

31021218 is an abundant number, since it is smaller than the sum of its proper divisors (39820410).

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

31021218 is a wasteful number, since it uses less digits than its factorization.

31021218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3680 (or 3671 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 31021218 is about 5569.6694695466. The cubic root of 31021218 is about 314.2097196621.

It can be divided in two parts, 310 and 21218, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 31021218 in words is "thirty-one million, twenty-one thousand, two hundred eighteen".