311331221 has 2 divisors, whose sum is σ = 311331222. Its totient is φ = 311331220.

The previous prime is 311331191. The next prime is 311331239. The reversal of 311331221 is 122133113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 213598225 + 97732996 = 14615^2 + 9886^2 .

It is an emirp because it is prime and its reverse (122133113) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-311331221 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 311331221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (311331281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155665610 + 155665611.

It is an arithmetic number, because the mean of its divisors is an integer number (155665611).

Almost surely, 2^311331221 is an apocalyptic number.

It is an amenable number.

311331221 is a deficient number, since it is larger than the sum of its proper divisors (1).

311331221 is an equidigital number, since it uses as much as digits as its factorization.

311331221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108, while the sum is 17.

The square root of 311331221 is about 17644.5804994055. The cubic root of 311331221 is about 677.7573327455.

Adding to 311331221 its reverse (122133113), we get a palindrome (433464334).

The spelling of 311331221 in words is "three hundred eleven million, three hundred thirty-one thousand, two hundred twenty-one".