31231320021 has 12 divisors (see below), whose sum is σ = 49212989280. Its totient is φ = 18928072680.

The previous prime is 31231319989. The next prime is 31231320049. The reversal of 31231320021 is 12002313213.

31231320021 is a `hidden beast` number, since 312 + 31 + 320 + 0 + 2 + 1 = 666.

It is not a de Polignac number, because 31231320021 - 2⁵ = 31231319989 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 31231319976 and 31231320003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31231820021) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 157733841 + ... + 157734038.

It is an arithmetic number, because the mean of its divisors is an integer number (4101082440).

Almost surely, 2^31231320021 is an apocalyptic number.

It is an amenable number.

31231320021 is a deficient number, since it is larger than the sum of its proper divisors (17981669259).

31231320021 is a wasteful number, since it uses less digits than its factorization.

31231320021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315467896 (or 315467893 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

Adding to 31231320021 its reverse (12002313213), we get a palindrome (43233633234).

The spelling of 31231320021 in words is "thirty-one billion, two hundred thirty-one million, three hundred twenty thousand, twenty-one".