31686342221 has 2 divisors, whose sum is σ = 31686342222. Its totient is φ = 31686342220.

The previous prime is 31686342203. The next prime is 31686342257. The reversal of 31686342221 is 12224368613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31112020996 + 574321225 = 176386^2 + 23965^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31686342221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31686312221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15843171110 + 15843171111.

It is an arithmetic number, because the mean of its divisors is an integer number (15843171111).

Almost surely, 2^31686342221 is an apocalyptic number.

It is an amenable number.

31686342221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31686342221 is an equidigital number, since it uses as much as digits as its factorization.

31686342221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 82944, while the sum is 38.

The spelling of 31686342221 in words is "thirty-one billion, six hundred eighty-six million, three hundred forty-two thousand, two hundred twenty-one".