31121213220 has 72 divisors (see below), whose sum is σ = 95283324864. Its totient is φ = 8221424448.

The previous prime is 31121213209. The next prime is 31121213293. The reversal of 31121213220 is 2231212113.

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 = 31121213193 and 31121213202.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 788664 + ... + 827183.

It is an arithmetic number, because the mean of its divisors is an integer number (1323379512).

Almost surely, 2^31121213220 is an apocalyptic number.

31121213220 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

31121213220 is an abundant number, since it is smaller than the sum of its proper divisors (64162111644).

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

31121213220 is a wasteful number, since it uses less digits than its factorization.

31121213220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1615969 (or 1615964 counting only the distinct ones).

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

Adding to 31121213220 its reverse (2231212113), we get a palindrome (33352425333).

The spelling of 31121213220 in words is "thirty-one billion, one hundred twenty-one million, two hundred thirteen thousand, two hundred twenty".