31686991 has 8 divisors (see below), whose sum is σ = 37382144. Its totient is φ = 26283960.

The previous prime is 31686989. The next prime is 31687013. The reversal of 31686991 is 19968613.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 31686991 - 2¹ = 31686989 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 (31686901) 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 7 ways as a sum of consecutive naturals, for example, 72795 + ... + 73228.

It is an arithmetic number, because the mean of its divisors is an integer number (4672768).

Almost surely, 2^31686991 is an apocalyptic number.

31686991 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

31686991 is a deficient number, since it is larger than the sum of its proper divisors (5695153).

31686991 is a wasteful number, since it uses less digits than its factorization.

31686991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146061.

The product of its digits is 69984, while the sum is 43.

The square root of 31686991 is about 5629.1199134501. The cubic root of 31686991 is about 316.4416692898.

The spelling of 31686991 in words is "thirty-one million, six hundred eighty-six thousand, nine hundred ninety-one".