31131122220 has 72 divisors (see below), whose sum is σ = 103015720080. Its totient is φ = 7546938240.

The previous prime is 31131122189. The next prime is 31131122227. The reversal of 31131122220 is 2222113113.

31131122220 is a `hidden beast` number, since 311 + 311 + 2 + 22 + 20 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 31131122193 and 31131122202.

It is not an unprimeable number, because it can be changed into a prime (31131122227) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7859415 + ... + 7863374.

It is an arithmetic number, because the mean of its divisors is an integer number (1430773890).

Almost surely, 2^31131122220 is an apocalyptic number.

31131122220 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

31131122220 is an abundant number, since it is smaller than the sum of its proper divisors (71884597860).

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

31131122220 is a wasteful number, since it uses less digits than its factorization.

31131122220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15722815 (or 15722810 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

Adding to 31131122220 its reverse (2222113113), we get a palindrome (33353235333).

It can be divided in two parts, 31131 and 122220, that added together give a palindrome (153351).

The spelling of 31131122220 in words is "thirty-one billion, one hundred thirty-one million, one hundred twenty-two thousand, two hundred twenty".