31131220 has 12 divisors (see below), whose sum is σ = 65375604. Its totient is φ = 12452480.

The previous prime is 31131211. The next prime is 31131227. The reversal of 31131220 is 2213113.

It can be written as a sum of positive squares in 2 ways, for example, as 22905796 + 8225424 = 4786^2 + 2868^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 31131220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31131227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 778261 + ... + 778300.

It is an arithmetic number, because the mean of its divisors is an integer number (5447967).

Almost surely, 2^31131220 is an apocalyptic number.

It is an amenable number.

31131220 is an abundant number, since it is smaller than the sum of its proper divisors (34244384).

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

31131220 is a wasteful number, since it uses less digits than its factorization.

31131220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1556570 (or 1556568 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 31131220 is about 5579.5358229874. The cubic root of 31131220 is about 314.5806799868.

Adding to 31131220 its reverse (2213113), we get a palindrome (33344333).

The spelling of 31131220 in words is "thirty-one million, one hundred thirty-one thousand, two hundred twenty".