31231220 has 24 divisors (see below), whose sum is σ = 66239208. Its totient is φ = 12368000.

The previous prime is 31231139. The next prime is 31231223. The reversal of 31231220 is 2213213.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 6091024 + 25140196 = 2468^2 + 5014^2 .

It is a junction number, because it is equal to n+sod(n) for n = 31231195 and 31231204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31231223) 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, 5711 + ... + 9750.

It is an arithmetic number, because the mean of its divisors is an integer number (2759967).

Almost surely, 2^31231220 is an apocalyptic number.

It is an amenable number.

31231220 is an abundant number, since it is smaller than the sum of its proper divisors (35007988).

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

31231220 is a wasteful number, since it uses less digits than its factorization.

31231220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15571 (or 15569 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 31231220 is about 5588.4899570456. The cubic root of 31231220 is about 314.9171529838.

Adding to 31231220 its reverse (2213213), we get a palindrome (33444433).

The spelling of 31231220 in words is "thirty-one million, two hundred thirty-one thousand, two hundred twenty".