31335721 has 2 divisors, whose sum is σ = 31335722. Its totient is φ = 31335720.

The previous prime is 31335719. The next prime is 31335727. The reversal of 31335721 is 12753313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26925721 + 4410000 = 5189^2 + 2100^2 .

It is a cyclic number.

It is not a de Polignac number, because 31335721 - 2¹ = 31335719 is a prime.

Together with 31335719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (31335727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15667860 + 15667861.

It is an arithmetic number, because the mean of its divisors is an integer number (15667861).

Almost surely, 2^31335721 is an apocalyptic number.

It is an amenable number.

31335721 is a deficient number, since it is larger than the sum of its proper divisors (1).

31335721 is an equidigital number, since it uses as much as digits as its factorization.

31335721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1890, while the sum is 25.

The square root of 31335721 is about 5597.8318124074. The cubic root of 31335721 is about 315.2680040481.

The spelling of 31335721 in words is "thirty-one million, three hundred thirty-five thousand, seven hundred twenty-one".