643517257 has 4 divisors (see below), whose sum is σ = 645807636. Its totient is φ = 641226880.

The previous prime is 643517219. The next prime is 643517267. The reversal of 643517257 is 752715346.

643517257 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 371564176 + 271953081 = 19276^2 + 16491^2 .

It is a cyclic number.

It is not a de Polignac number, because 643517257 - 2²³ = 635128649 is a prime.

It is a super-2 number, since 2×643517257² = 828228920113608098, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643517267) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1144768 + ... + 1145329.

It is an arithmetic number, because the mean of its divisors is an integer number (161451909).

Almost surely, 2^643517257 is an apocalyptic number.

It is an amenable number.

643517257 is a deficient number, since it is larger than the sum of its proper divisors (2290379).

643517257 is a wasteful number, since it uses less digits than its factorization.

643517257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2290378.

The product of its digits is 176400, while the sum is 40.

The square root of 643517257 is about 25367.6419282518. The cubic root of 643517257 is about 863.3496804081.

The spelling of 643517257 in words is "six hundred forty-three million, five hundred seventeen thousand, two hundred fifty-seven".