31720399 has 4 divisors (see below), whose sum is σ = 31731840. Its totient is φ = 31708960.

The previous prime is 31720397. The next prime is 31720421. The reversal of 31720399 is 99302713.

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.

It is a cyclic number.

It is not a de Polignac number, because 31720399 - 2¹ = 31720397 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 (31720397) 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, 1362 + ... + 8080.

It is an arithmetic number, because the mean of its divisors is an integer number (7932960).

Almost surely, 2^31720399 is an apocalyptic number.

31720399 is a deficient number, since it is larger than the sum of its proper divisors (11441).

31720399 is an equidigital number, since it uses as much as digits as its factorization.

31720399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11440.

The product of its (nonzero) digits is 10206, while the sum is 34.

The square root of 31720399 is about 5632.0865582837. The cubic root of 31720399 is about 316.5528397296.

The spelling of 31720399 in words is "thirty-one million, seven hundred twenty thousand, three hundred ninety-nine".