31231030021 has 4 divisors (see below), whose sum is σ = 33068149452. Its totient is φ = 29393910592.

The previous prime is 31231030013. The next prime is 31231030027. The reversal of 31231030021 is 12003013213.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16138907521 + 15092122500 = 127039^2 + 122850^2 .

It is a cyclic number.

It is not a de Polignac number, because 31231030021 - 2³ = 31231030013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31231029977 and 31231030004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31231030027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 918559690 + ... + 918559723.

It is an arithmetic number, because the mean of its divisors is an integer number (8267037363).

Almost surely, 2^31231030021 is an apocalyptic number.

It is an amenable number.

31231030021 is a deficient number, since it is larger than the sum of its proper divisors (1837119431).

31231030021 is a wasteful number, since it uses less digits than its factorization.

31231030021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1837119430.

The product of its (nonzero) digits is 108, while the sum is 16.

Adding to 31231030021 its reverse (12003013213), we get a palindrome (43234043234).

The spelling of 31231030021 in words is "thirty-one billion, two hundred thirty-one million, thirty thousand, twenty-one".