31375317821 has 2 divisors, whose sum is σ = 31375317822. Its totient is φ = 31375317820.

The previous prime is 31375317817. The next prime is 31375317839. The reversal of 31375317821 is 12871357313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31325460100 + 49857721 = 176990^2 + 7061^2 .

It is a cyclic number.

It is not a de Polignac number, because 31375317821 - 2² = 31375317817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31375317851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15687658910 + 15687658911.

It is an arithmetic number, because the mean of its divisors is an integer number (15687658911).

Almost surely, 2^31375317821 is an apocalyptic number.

It is an amenable number.

31375317821 is a deficient number, since it is larger than the sum of its proper divisors (1).

31375317821 is an equidigital number, since it uses as much as digits as its factorization.

31375317821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 105840, while the sum is 41.

The spelling of 31375317821 in words is "thirty-one billion, three hundred seventy-five million, three hundred seventeen thousand, eight hundred twenty-one".