31661309 has 2 divisors, whose sum is σ = 31661310. Its totient is φ = 31661308.

The previous prime is 31661303. The next prime is 31661351. The reversal of 31661309 is 90316613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 29268100 + 2393209 = 5410^2 + 1547^2 .

It is a cyclic number.

It is not a de Polignac number, because 31661309 - 2⁸ = 31661053 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31661303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15830654 + 15830655.

It is an arithmetic number, because the mean of its divisors is an integer number (15830655).

Almost surely, 2^31661309 is an apocalyptic number.

It is an amenable number.

31661309 is a deficient number, since it is larger than the sum of its proper divisors (1).

31661309 is an equidigital number, since it uses as much as digits as its factorization.

31661309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2916, while the sum is 29.

The square root of 31661309 is about 5626.8382773988. The cubic root of 31661309 is about 316.3561552112.

The spelling of 31661309 in words is "thirty-one million, six hundred sixty-one thousand, three hundred nine".