31216391 has 2 divisors, whose sum is σ = 31216392. Its totient is φ = 31216390.

The previous prime is 31216343. The next prime is 31216397. The reversal of 31216391 is 19361213.

It is a strong prime.

It is an emirp because it is prime and its reverse (19361213) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31216391 - 2⁶ = 31216327 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31216391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31216397) 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 as a sum of consecutive naturals, namely, 15608195 + 15608196.

It is an arithmetic number, because the mean of its divisors is an integer number (15608196).

Almost surely, 2^31216391 is an apocalyptic number.

31216391 is a deficient number, since it is larger than the sum of its proper divisors (1).

31216391 is an equidigital number, since it uses as much as digits as its factorization.

31216391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 972, while the sum is 26.

The square root of 31216391 is about 5587.1630547175. The cubic root of 31216391 is about 314.8673028043.

The spelling of 31216391 in words is "thirty-one million, two hundred sixteen thousand, three hundred ninety-one".