31681399 has 4 divisors (see below), whose sum is σ = 31692664. Its totient is φ = 31670136.

The previous prime is 31681393. The next prime is 31681457. The reversal of 31681399 is 99318613.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 99318613 = 787 ⋅126199.

It is a cyclic number.

It is not a de Polignac number, because 31681399 - 2⁵ = 31681367 is a prime.

It is a super-2 number, since 2×31681399² = 2007422085194402, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31681393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2524 + ... + 8350.

It is an arithmetic number, because the mean of its divisors is an integer number (7923166).

Almost surely, 2^31681399 is an apocalyptic number.

31681399 is a deficient number, since it is larger than the sum of its proper divisors (11265).

31681399 is an equidigital number, since it uses as much as digits as its factorization.

31681399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11264.

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

The square root of 31681399 is about 5628.6231886670. The cubic root of 31681399 is about 316.4230533861.

The spelling of 31681399 in words is "thirty-one million, six hundred eighty-one thousand, three hundred ninety-nine".