643875506 has 4 divisors (see below), whose sum is σ = 965813262. Its totient is φ = 321937752.

The previous prime is 643875481. The next prime is 643875509. The reversal of 643875506 is 605578346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 605578346 = 2 ⋅302789173.

It can be written as a sum of positive squares in only one way, i.e., 636805225 + 7070281 = 25235^2 + 2659^2 .

It is not an unprimeable number, because it can be changed into a prime (643875509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160968875 + ... + 160968878.

Almost surely, 2^643875506 is an apocalyptic number.

643875506 is a deficient number, since it is larger than the sum of its proper divisors (321937756).

643875506 is a wasteful number, since it uses less digits than its factorization.

643875506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321937755.

The product of its (nonzero) digits is 604800, while the sum is 44.

The square root of 643875506 is about 25374.7020869211. The cubic root of 643875506 is about 863.5098609259.

The spelling of 643875506 in words is "six hundred forty-three million, eight hundred seventy-five thousand, five hundred six".