311331220021 has 2 divisors, whose sum is σ = 311331220022. Its totient is φ = 311331220020.

The previous prime is 311331219973. The next prime is 311331220037. The reversal of 311331220021 is 120022133113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 211035496996 + 100295723025 = 459386^2 + 316695^2 .

It is a cyclic number.

It is not a de Polignac number, because 311331220021 - 2⁷ = 311331219893 is a prime.

It is a super-2 number, since 2×311331220021² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (315331220021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155665610010 + 155665610011.

It is an arithmetic number, because the mean of its divisors is an integer number (155665610011).

Almost surely, 2^311331220021 is an apocalyptic number.

It is an amenable number.

311331220021 is a deficient number, since it is larger than the sum of its proper divisors (1).

311331220021 is an equidigital number, since it uses as much as digits as its factorization.

311331220021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 216, while the sum is 19.

Adding to 311331220021 its reverse (120022133113), we get a palindrome (431353353134).

The spelling of 311331220021 in words is "three hundred eleven billion, three hundred thirty-one million, two hundred twenty thousand, twenty-one".