31131212121 has 12 divisors (see below), whose sum is σ = 45005014548. Its totient is φ = 20736737664.

The previous prime is 31131212083. The next prime is 31131212143. The reversal of 31131212121 is 12121213113.

31131212121 is a `hidden beast` number, since 311 + 312 + 1 + 21 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 15770336400 + 15360875721 = 125580^2 + 123939^2 .

It is not a de Polignac number, because 31131212121 - 2⁹ = 31131211609 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31131212094 and 31131212103.

It is not an unprimeable number, because it can be changed into a prime (31131252121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1438980 + ... + 1460453.

It is an arithmetic number, because the mean of its divisors is an integer number (3750417879).

Almost surely, 2^31131212121 is an apocalyptic number.

It is an amenable number.

31131212121 is a deficient number, since it is larger than the sum of its proper divisors (13873802427).

31131212121 is a wasteful number, since it uses less digits than its factorization.

31131212121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2900632 (or 2900629 counting only the distinct ones).

The product of its digits is 72, while the sum is 18.

Adding to 31131212121 its reverse (12121213113), we get a palindrome (43252425234).

The spelling of 31131212121 in words is "thirty-one billion, one hundred thirty-one million, two hundred twelve thousand, one hundred twenty-one".