31213213 has 2 divisors, whose sum is σ = 31213214. Its totient is φ = 31213212.

The previous prime is 31213211. The next prime is 31213243. The reversal of 31213213 is 31231213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15705369 + 15507844 = 3963^2 + 3938^2 .

It is a cyclic number.

It is not a de Polignac number, because 31213213 - 2¹ = 31213211 is a prime.

Together with 31213211, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31213211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15606606 + 15606607.

It is an arithmetic number, because the mean of its divisors is an integer number (15606607).

Almost surely, 2^31213213 is an apocalyptic number.

It is an amenable number.

31213213 is a deficient number, since it is larger than the sum of its proper divisors (1).

31213213 is an equidigital number, since it uses as much as digits as its factorization.

31213213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108, while the sum is 16.

The square root of 31213213 is about 5586.8786455408. The cubic root of 31213213 is about 314.8566173682.

Adding to 31213213 its reverse (31231213), we get a palindrome (62444426).

The spelling of 31213213 in words is "thirty-one million, two hundred thirteen thousand, two hundred thirteen".