31200000021 has 24 divisors (see below), whose sum is σ = 45397421784. Its totient is φ = 20647895040.

The previous prime is 31200000017. The next prime is 31200000031. The reversal of 31200000021 is 12000000213.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2373053796 + 28826946225 = 48714^2 + 169785^2 .

It is not a de Polignac number, because 31200000021 - 2² = 31200000017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 31199999949 and 31200000012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31200000031) 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, 664885 + ... + 710261.

It is an arithmetic number, because the mean of its divisors is an integer number (1891559241).

Almost surely, 2^31200000021 is an apocalyptic number.

It is an amenable number.

31200000021 is a deficient number, since it is larger than the sum of its proper divisors (14197421763).

31200000021 is a wasteful number, since it uses less digits than its factorization.

31200000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45941 (or 45938 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

Adding to 31200000021 its reverse (12000000213), we get a palindrome (43200000234).

It can be divided in two parts, 3 and 1200000021, that multiplied together give a palindrome (3600000063).

The spelling of 31200000021 in words is "thirty-one billion, two hundred million, twenty-one", and thus it is an aban number.