311221213 has 2 divisors, whose sum is σ = 311221214. Its totient is φ = 311221212.

The previous prime is 311221181. The next prime is 311221223. The reversal of 311221213 is 312122113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 308458969 + 2762244 = 17563^2 + 1662^2 .

It is a cyclic number.

It is not a de Polignac number, because 311221213 - 2⁵ = 311221181 is a prime.

It is a super-3 number, since 3×311221213³ (a number of 26 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (311221223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155610606 + 155610607.

It is an arithmetic number, because the mean of its divisors is an integer number (155610607).

Almost surely, 2^311221213 is an apocalyptic number.

It is an amenable number.

311221213 is a deficient number, since it is larger than the sum of its proper divisors (1).

311221213 is an equidigital number, since it uses as much as digits as its factorization.

311221213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72, while the sum is 16.

The square root of 311221213 is about 17641.4628928556. The cubic root of 311221213 is about 677.6774954671.

Adding to 311221213 its reverse (312122113), we get a palindrome (623343326).

The spelling of 311221213 in words is "three hundred eleven million, two hundred twenty-one thousand, two hundred thirteen".