31213220 has 24 divisors (see below), whose sum is σ = 65899008. Its totient is φ = 12418400.

The previous prime is 31213213. The next prime is 31213243. The reversal of 31213220 is 2231213.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 31213195 and 31213204.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 266 + ... + 7905.

It is an arithmetic number, because the mean of its divisors is an integer number (2745792).

Almost surely, 2^31213220 is an apocalyptic number.

It is an amenable number.

31213220 is an abundant number, since it is smaller than the sum of its proper divisors (34685788).

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

31213220 is a wasteful number, since it uses less digits than its factorization.

31213220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8371 (or 8369 counting only the distinct ones).

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

The square root of 31213220 is about 5586.8792720087. The cubic root of 31213220 is about 314.8566409052.

Adding to 31213220 its reverse (2231213), we get a palindrome (33444433).

The spelling of 31213220 in words is "thirty-one million, two hundred thirteen thousand, two hundred twenty".