31505921 has 2 divisors, whose sum is σ = 31505922. Its totient is φ = 31505920.

The previous prime is 31505909. The next prime is 31505923. The reversal of 31505921 is 12950513.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21520321 + 9985600 = 4639^2 + 3160^2 .

It is a cyclic number.

It is not a de Polignac number, because 31505921 - 2¹⁸ = 31243777 is a prime.

Together with 31505923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (31505923) 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, 15752960 + 15752961.

It is an arithmetic number, because the mean of its divisors is an integer number (15752961).

Almost surely, 2^31505921 is an apocalyptic number.

It is an amenable number.

31505921 is a deficient number, since it is larger than the sum of its proper divisors (1).

31505921 is an equidigital number, since it uses as much as digits as its factorization.

31505921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 31505921 is about 5613.0135399801. The cubic root of 31505921 is about 315.8377665612.

The spelling of 31505921 in words is "thirty-one million, five hundred five thousand, nine hundred twenty-one".