31993861 has 4 divisors (see below), whose sum is σ = 32063724. Its totient is φ = 31924000.

The previous prime is 31993823. The next prime is 31993867. The reversal of 31993861 is 16839913.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16839913 = 31 ⋅543223.

It can be written as a sum of positive squares in 2 ways, for example, as 15752961 + 16240900 = 3969^2 + 4030^2 .

It is a cyclic number.

It is not a de Polignac number, because 31993861 - 2⁹ = 31993349 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 (31993867) 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, 34240 + ... + 35161.

It is an arithmetic number, because the mean of its divisors is an integer number (8015931).

Almost surely, 2^31993861 is an apocalyptic number.

It is an amenable number.

31993861 is a deficient number, since it is larger than the sum of its proper divisors (69863).

31993861 is an equidigital number, since it uses as much as digits as its factorization.

31993861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69862.

The product of its digits is 34992, while the sum is 40.

The square root of 31993861 is about 5656.3116073993. The cubic root of 31993861 is about 317.4599068972.

The spelling of 31993861 in words is "thirty-one million, nine hundred ninety-three thousand, eight hundred sixty-one".