31997509 has 4 divisors (see below), whose sum is σ = 32017516. Its totient is φ = 31977504.

The previous prime is 31997477. The next prime is 31997513. The reversal of 31997509 is 90579913.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 390625 + 31606884 = 625^2 + 5622^2 .

It is a cyclic number.

It is not a de Polignac number, because 31997509 - 2⁵ = 31997477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31997569) 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 in 3 ways as a sum of consecutive naturals, for example, 7374 + ... + 10879.

It is an arithmetic number, because the mean of its divisors is an integer number (8004379).

Almost surely, 2^31997509 is an apocalyptic number.

It is an amenable number.

31997509 is a deficient number, since it is larger than the sum of its proper divisors (20007).

31997509 is a wasteful number, since it uses less digits than its factorization.

31997509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20006.

The product of its (nonzero) digits is 76545, while the sum is 43.

The square root of 31997509 is about 5656.6340698334. The cubic root of 31997509 is about 317.4719722298.

The spelling of 31997509 in words is "thirty-one million, nine hundred ninety-seven thousand, five hundred nine".