31320391 has 2 divisors, whose sum is σ = 31320392. Its totient is φ = 31320390.

The previous prime is 31320347. The next prime is 31320413. The reversal of 31320391 is 19302313.

It is an a-pointer prime, because the next prime (31320413) can be obtained adding 31320391 to its sum of digits (22).

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31320391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31320491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15660195 + 15660196.

It is an arithmetic number, because the mean of its divisors is an integer number (15660196).

Almost surely, 2^31320391 is an apocalyptic number.

31320391 is a deficient number, since it is larger than the sum of its proper divisors (1).

31320391 is an equidigital number, since it uses as much as digits as its factorization.

31320391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 22.

The square root of 31320391 is about 5596.4623647444. The cubic root of 31320391 is about 315.2165840637.

The spelling of 31320391 in words is "thirty-one million, three hundred twenty thousand, three hundred ninety-one".