31031621 has 2 divisors, whose sum is σ = 31031622. Its totient is φ = 31031620.

The previous prime is 31031599. The next prime is 31031657. The reversal of 31031621 is 12613013.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30129121 + 902500 = 5489^2 + 950^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31031621 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31031621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31031821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15515810 + 15515811.

It is an arithmetic number, because the mean of its divisors is an integer number (15515811).

Almost surely, 2^31031621 is an apocalyptic number.

It is an amenable number.

31031621 is a deficient number, since it is larger than the sum of its proper divisors (1).

31031621 is an equidigital number, since it uses as much as digits as its factorization.

31031621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 31031621 is about 5570.6032886932. The cubic root of 31031621 is about 314.2448392631.

Adding to 31031621 its reverse (12613013), we get a palindrome (43644634).

The spelling of 31031621 in words is "thirty-one million, thirty-one thousand, six hundred twenty-one".