646297921 has 2 divisors, whose sum is σ = 646297922. Its totient is φ = 646297920.

The previous prime is 646297919. The next prime is 646297933. The reversal of 646297921 is 129792646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 472453696 + 173844225 = 21736^2 + 13185^2 .

It is a cyclic number.

It is not a de Polignac number, because 646297921 - 2¹ = 646297919 is a prime.

Together with 646297919, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (646297961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323148960 + 323148961.

It is an arithmetic number, because the mean of its divisors is an integer number (323148961).

Almost surely, 2^646297921 is an apocalyptic number.

It is an amenable number.

646297921 is a deficient number, since it is larger than the sum of its proper divisors (1).

646297921 is an equidigital number, since it uses as much as digits as its factorization.

646297921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 46.

The square root of 646297921 is about 25422.3901512033. The cubic root of 646297921 is about 864.5914165114.

The spelling of 646297921 in words is "six hundred forty-six million, two hundred ninety-seven thousand, nine hundred twenty-one".