311231021 has 2 divisors, whose sum is σ = 311231022. Its totient is φ = 311231020.

The previous prime is 311231017. The next prime is 311231023. The reversal of 311231021 is 120132113.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 267486025 + 43744996 = 16355^2 + 6614^2 .

It is an emirp because it is prime and its reverse (120132113) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 311231021 - 2² = 311231017 is a prime.

Together with 311231023, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 311230987 and 311231005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (311231023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155615510 + 155615511.

It is an arithmetic number, because the mean of its divisors is an integer number (155615511).

Almost surely, 2^311231021 is an apocalyptic number.

It is an amenable number.

311231021 is a deficient number, since it is larger than the sum of its proper divisors (1).

311231021 is an equidigital number, since it uses as much as digits as its factorization.

311231021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 311231021 is about 17641.7408721475. The cubic root of 311231021 is about 677.6846142953.

Adding to 311231021 its reverse (120132113), we get a palindrome (431363134).

The spelling of 311231021 in words is "three hundred eleven million, two hundred thirty-one thousand, twenty-one".