31311203220221 has 2 divisors, whose sum is σ = 31311203220222. Its totient is φ = 31311203220220.

The previous prime is 31311203220217. The next prime is 31311203220289. The reversal of 31311203220221 is 12202230211313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28400255397721 + 2910947822500 = 5329189^2 + 1706150^2 .

It is a cyclic number.

It is not a de Polignac number, because 31311203220221 - 2² = 31311203220217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31311203220211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15655601610110 + 15655601610111.

It is an arithmetic number, because the mean of its divisors is an integer number (15655601610111).

Almost surely, 2^{31311203220221} is an apocalyptic number.

It is an amenable number.

31311203220221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31311203220221 is an equidigital number, since it uses as much as digits as its factorization.

31311203220221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 23.

Adding to 31311203220221 its reverse (12202230211313), we get a palindrome (43513433431534).

The spelling of 31311203220221 in words is "thirty-one trillion, three hundred eleven billion, two hundred three million, two hundred twenty thousand, two hundred twenty-one".