31991691 has 8 divisors (see below), whose sum is σ = 42693840. Its totient is φ = 21308672.

The previous prime is 31991683. The next prime is 31991693. The reversal of 31991691 is 19619913.

It is a happy number.

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 31991691 - 2³ = 31991683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31991693) 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, 270 + ... + 8003.

It is an arithmetic number, because the mean of its divisors is an integer number (5336730).

Almost surely, 2^31991691 is an apocalyptic number.

31991691 is a deficient number, since it is larger than the sum of its proper divisors (10702149).

31991691 is a wasteful number, since it uses less digits than its factorization.

31991691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9565.

The product of its digits is 13122, while the sum is 39.

The square root of 31991691 is about 5656.1197830315. The cubic root of 31991691 is about 317.4527294413.

The spelling of 31991691 in words is "thirty-one million, nine hundred ninety-one thousand, six hundred ninety-one".