315320821 has 2 divisors, whose sum is σ = 315320822. Its totient is φ = 315320820.

The previous prime is 315320779. The next prime is 315320867. The reversal of 315320821 is 128023513.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 173448900 + 141871921 = 13170^2 + 11911^2 .

It is a cyclic number.

It is not a de Polignac number, because 315320821 - 2¹⁵ = 315288053 is a prime.

It is a super-2 number, since 2×315320821² = 198854440312228082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (315326821) 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, 157660410 + 157660411.

It is an arithmetic number, because the mean of its divisors is an integer number (157660411).

Almost surely, 2^315320821 is an apocalyptic number.

It is an amenable number.

315320821 is a deficient number, since it is larger than the sum of its proper divisors (1).

315320821 is an equidigital number, since it uses as much as digits as its factorization.

315320821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 315320821 is about 17757.2751569603. The cubic root of 315320821 is about 680.6401274660.

The spelling of 315320821 in words is "three hundred fifteen million, three hundred twenty thousand, eight hundred twenty-one".