31997909 has 2 divisors, whose sum is σ = 31997910. Its totient is φ = 31997908.

The previous prime is 31997887. The next prime is 31997963. The reversal of 31997909 is 90979913.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18879025 + 13118884 = 4345^2 + 3622^2 .

It is an emirp because it is prime and its reverse (90979913) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31997909 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31997989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15998954 + 15998955.

It is an arithmetic number, because the mean of its divisors is an integer number (15998955).

Almost surely, 2^31997909 is an apocalyptic number.

It is an amenable number.

31997909 is a deficient number, since it is larger than the sum of its proper divisors (1).

31997909 is an equidigital number, since it uses as much as digits as its factorization.

31997909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 137781, while the sum is 47.

The square root of 31997909 is about 5656.6694264381. The cubic root of 31997909 is about 317.4732951272.

The spelling of 31997909 in words is "thirty-one million, nine hundred ninety-seven thousand, nine hundred nine".