631561213 has 2 divisors, whose sum is σ = 631561214. Its totient is φ = 631561212.

The previous prime is 631561211. The next prime is 631561223. The reversal of 631561213 is 312165136.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 489427129 + 142134084 = 22123^2 + 11922^2 .

It is a cyclic number.

It is not a de Polignac number, because 631561213 - 2¹ = 631561211 is a prime.

Together with 631561211, 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 (631561211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 315780606 + 315780607.

It is an arithmetic number, because the mean of its divisors is an integer number (315780607).

Almost surely, 2^631561213 is an apocalyptic number.

It is an amenable number.

631561213 is a deficient number, since it is larger than the sum of its proper divisors (1).

631561213 is an equidigital number, since it uses as much as digits as its factorization.

631561213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3240, while the sum is 28.

The square root of 631561213 is about 25130.8816598224. The cubic root of 631561213 is about 857.9694355223.

It can be divided in two parts, 6315 and 61213, that added together give a triangular number (67528 = T₃₆₇).

The spelling of 631561213 in words is "six hundred thirty-one million, five hundred sixty-one thousand, two hundred thirteen".