31399213 has 2 divisors, whose sum is σ = 31399214. Its totient is φ = 31399212.

The previous prime is 31399211. The next prime is 31399223. The reversal of 31399213 is 31299313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21178404 + 10220809 = 4602^2 + 3197^2 .

It is a cyclic number.

It is not a de Polignac number, because 31399213 - 2¹ = 31399211 is a prime.

Together with 31399211, it forms a pair of twin primes.

It is the 5604-th Hogben number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31399211) by changing a digit.

It is a nontrivial repunit in base 5603.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15699606 + 15699607.

It is an arithmetic number, because the mean of its divisors is an integer number (15699607).

Almost surely, 2^31399213 is an apocalyptic number.

It is an amenable number.

31399213 is a deficient number, since it is larger than the sum of its proper divisors (1).

31399213 is an equidigital number, since it uses as much as digits as its factorization.

31399213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4374, while the sum is 31.

The square root of 31399213 is about 5603.5000669225. The cubic root of 31399213 is about 315.4807909389.

The spelling of 31399213 in words is "thirty-one million, three hundred ninety-nine thousand, two hundred thirteen".