31391988 has 12 divisors (see below), whose sum is σ = 73248000. Its totient is φ = 10463992.

The previous prime is 31391957. The next prime is 31391989. The reversal of 31391988 is 88919313.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31391989) 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, 1307988 + ... + 1308011.

It is an arithmetic number, because the mean of its divisors is an integer number (6104000).

Almost surely, 2^31391988 is an apocalyptic number.

It is an amenable number.

31391988 is an abundant number, since it is smaller than the sum of its proper divisors (41856012).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

31391988 is a wasteful number, since it uses less digits than its factorization.

31391988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2616006 (or 2616004 counting only the distinct ones).

The product of its digits is 46656, while the sum is 42.

The square root of 31391988 is about 5602.8553434834. The cubic root of 31391988 is about 315.4565915684.

The spelling of 31391988 in words is "thirty-one million, three hundred ninety-one thousand, nine hundred eighty-eight".