31999987 has 4 divisors (see below), whose sum is σ = 32137560. Its totient is φ = 31862416.

The previous prime is 31999939. The next prime is 32000011. The reversal of 31999987 is 78999913.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31999987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31999907) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68437 + ... + 68902.

It is an arithmetic number, because the mean of its divisors is an integer number (8034390).

Almost surely, 2^31999987 is an apocalyptic number.

31999987 is a deficient number, since it is larger than the sum of its proper divisors (137573).

31999987 is a wasteful number, since it uses less digits than its factorization.

31999987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137572.

The product of its digits is 1102248, while the sum is 55.

The square root of 31999987 is about 5656.8531004437. The cubic root of 31999987 is about 317.4801674015.

The spelling of 31999987 in words is "thirty-one million, nine hundred ninety-nine thousand, nine hundred eighty-seven".