31561166432221 has 2 divisors, whose sum is σ = 31561166432222. Its totient is φ = 31561166432220.

The previous prime is 31561166432203. The next prime is 31561166432261. The reversal of 31561166432221 is 12223466116513.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17296865102500 + 14264301329721 = 4158950^2 + 3776811^2 .

It is a cyclic number.

It is not a de Polignac number, because 31561166432221 - 2⁷ = 31561166432093 is a prime.

It is a super-2 number, since 2×31561166432221² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31561166432261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15780583216110 + 15780583216111.

It is an arithmetic number, because the mean of its divisors is an integer number (15780583216111).

Almost surely, 2^{31561166432221} is an apocalyptic number.

It is an amenable number.

31561166432221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31561166432221 is an equidigital number, since it uses as much as digits as its factorization.

31561166432221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 43.

The spelling of 31561166432221 in words is "thirty-one trillion, five hundred sixty-one billion, one hundred sixty-six million, four hundred thirty-two thousand, two hundred twenty-one".