643404257 has 2 divisors, whose sum is σ = 643404258. Its totient is φ = 643404256.

The previous prime is 643404221. The next prime is 643404269. The reversal of 643404257 is 752404346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 411116176 + 232288081 = 20276^2 + 15241^2 .

It is a cyclic number.

It is not a de Polignac number, because 643404257 - 2¹⁴ = 643387873 is a prime.

It is not a weakly prime, because it can be changed into another prime (643404217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321702128 + 321702129.

It is an arithmetic number, because the mean of its divisors is an integer number (321702129).

Almost surely, 2^643404257 is an apocalyptic number.

It is an amenable number.

643404257 is a deficient number, since it is larger than the sum of its proper divisors (1).

643404257 is an equidigital number, since it uses as much as digits as its factorization.

643404257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 80640, while the sum is 35.

The square root of 643404257 is about 25365.4145836412. The cubic root of 643404257 is about 863.2991434444.

The spelling of 643404257 in words is "six hundred forty-three million, four hundred four thousand, two hundred fifty-seven".