31213987 has 4 divisors (see below), whose sum is σ = 35673136. Its totient is φ = 26754840.

The previous prime is 31213981. The next prime is 31213999. The reversal of 31213987 is 78931213.

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

It is not a de Polignac number, because 31213987 - 2⁷ = 31213859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31213981) 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, 2229564 + ... + 2229577.

It is an arithmetic number, because the mean of its divisors is an integer number (8918284).

Almost surely, 2^31213987 is an apocalyptic number.

31213987 is a deficient number, since it is larger than the sum of its proper divisors (4459149).

31213987 is an equidigital number, since it uses as much as digits as its factorization.

31213987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4459148.

The product of its digits is 9072, while the sum is 34.

The square root of 31213987 is about 5586.9479145594. The cubic root of 31213987 is about 314.8592198666.

The spelling of 31213987 in words is "thirty-one million, two hundred thirteen thousand, nine hundred eighty-seven".