31213209991 has 2 divisors, whose sum is σ = 31213209992. Its totient is φ = 31213209990.

The previous prime is 31213209889. The next prime is 31213210037. The reversal of 31213209991 is 19990231213.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 31213209991 - 2⁹ = 31213209479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31213201991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15606604995 + 15606604996.

It is an arithmetic number, because the mean of its divisors is an integer number (15606604996).

Almost surely, 2^31213209991 is an apocalyptic number.

31213209991 is a deficient number, since it is larger than the sum of its proper divisors (1).

31213209991 is an equidigital number, since it uses as much as digits as its factorization.

31213209991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26244, while the sum is 40.

The spelling of 31213209991 in words is "thirty-one billion, two hundred thirteen million, two hundred nine thousand, nine hundred ninety-one".