646385921 has 2 divisors, whose sum is σ = 646385922. Its totient is φ = 646385920.

The previous prime is 646385903. The next prime is 646385941. The reversal of 646385921 is 129583646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 444745921 + 201640000 = 21089^2 + 14200^2 .

It is a cyclic number.

It is not a de Polignac number, because 646385921 - 2²² = 642191617 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (646385941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323192960 + 323192961.

It is an arithmetic number, because the mean of its divisors is an integer number (323192961).

Almost surely, 2^646385921 is an apocalyptic number.

It is an amenable number.

646385921 is a deficient number, since it is larger than the sum of its proper divisors (1).

646385921 is an equidigital number, since it uses as much as digits as its factorization.

646385921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 44.

The square root of 646385921 is about 25424.1208500904. The cubic root of 646385921 is about 864.6306556864.

The spelling of 646385921 in words is "six hundred forty-six million, three hundred eighty-five thousand, nine hundred twenty-one".