31121321220 has 144 divisors (see below), whose sum is σ = 104926715712. Its totient is φ = 7402187520.

The previous prime is 31121321207. The next prime is 31121321243. The reversal of 31121321220 is 2212312113.

31121321220 is a `hidden beast` number, since 3 + 1 + 121 + 321 + 220 = 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 = 31121321193 and 31121321202.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 43342 + ... + 253221.

It is an arithmetic number, because the mean of its divisors is an integer number (728657748).

Almost surely, 2^31121321220 is an apocalyptic number.

31121321220 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 31121321220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (52463357856).

31121321220 is an abundant number, since it is smaller than the sum of its proper divisors (73805394492).

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

31121321220 is a wasteful number, since it uses less digits than its factorization.

31121321220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296642 (or 296637 counting only the distinct ones).

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

Adding to 31121321220 its reverse (2212312113), we get a palindrome (33333633333).

The spelling of 31121321220 in words is "thirty-one billion, one hundred twenty-one million, three hundred twenty-one thousand, two hundred twenty".