31517989 has 4 divisors (see below), whose sum is σ = 31530924. Its totient is φ = 31505056.

The previous prime is 31517963. The next prime is 31517999. The reversal of 31517989 is 98971513.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 98971513 = 19 ⋅5209027.

It can be written as a sum of positive squares in 2 ways, for example, as 24453025 + 7064964 = 4945^2 + 2658^2 .

It is a cyclic number.

It is not a de Polignac number, because 31517989 - 2⁷ = 31517861 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 (31517909) 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, 1582 + ... + 8095.

It is an arithmetic number, because the mean of its divisors is an integer number (7882731).

Almost surely, 2^31517989 is an apocalyptic number.

It is an amenable number.

31517989 is a deficient number, since it is larger than the sum of its proper divisors (12935).

31517989 is an equidigital number, since it uses as much as digits as its factorization.

31517989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12934.

The product of its digits is 68040, while the sum is 43.

The square root of 31517989 is about 5614.0884389186. The cubic root of 31517989 is about 315.8780874860.

The spelling of 31517989 in words is "thirty-one million, five hundred seventeen thousand, nine hundred eighty-nine".