31821313 has 2 divisors, whose sum is σ = 31821314. Its totient is φ = 31821312.

The previous prime is 31821311. The next prime is 31821319. The reversal of 31821313 is 31312813.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 29235649 + 2585664 = 5407^2 + 1608^2 .

It is a cyclic number.

It is not a de Polignac number, because 31821313 - 2¹ = 31821311 is a prime.

It is a super-2 number, since 2×31821313² = 2025191922087938, which contains 22 as substring.

Together with 31821311, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (31821311) 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, 15910656 + 15910657.

It is an arithmetic number, because the mean of its divisors is an integer number (15910657).

Almost surely, 2^31821313 is an apocalyptic number.

It is an amenable number.

31821313 is a deficient number, since it is larger than the sum of its proper divisors (1).

31821313 is an equidigital number, since it uses as much as digits as its factorization.

31821313 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 22.

The square root of 31821313 is about 5641.0382909532. The cubic root of 31821313 is about 316.8881738600. Note that the first 3 decimals are identical.

Subtracting from 31821313 its product of digits (432), we obtain a square (31820881 = 5641²).

The spelling of 31821313 in words is "thirty-one million, eight hundred twenty-one thousand, three hundred thirteen".