31121220 has 96 divisors (see below), whose sum is σ = 99404928. Its totient is φ = 7206912.

The previous prime is 31121197. The next prime is 31121249. The reversal of 31121220 is 2212113.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 31121196 and 31121205.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12087 + ... + 14433.

It is an arithmetic number, because the mean of its divisors is an integer number (1035468).

Almost surely, 2^31121220 is an apocalyptic number.

31121220 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31121220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49702464).

31121220 is an abundant number, since it is smaller than the sum of its proper divisors (68283708).

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

31121220 is a wasteful number, since it uses less digits than its factorization.

31121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2389 (or 2387 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 31121220 is about 5578.6396191186. The cubic root of 31121220 is about 314.5469930781.

Adding to 31121220 its reverse (2212113), we get a palindrome (33333333).

The spelling of 31121220 in words is "thirty-one million, one hundred twenty-one thousand, two hundred twenty".