643963867 has 12 divisors (see below), whose sum is σ = 683264680. Its totient is φ = 606738528.

The previous prime is 643963847. The next prime is 643963871. The reversal of 643963867 is 768369346.

It is not a de Polignac number, because 643963867 - 2⁷ = 643963739 is a prime.

It is not an unprimeable number, because it can be changed into a prime (643963807) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 26359 + ... + 44527.

Almost surely, 2^643963867 is an apocalyptic number.

643963867 is a gapful number since it is divisible by the number (67) formed by its first and last digit.

643963867 is a deficient number, since it is larger than the sum of its proper divisors (39300813).

643963867 is a wasteful number, since it uses less digits than its factorization.

643963867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18282 (or 18259 counting only the distinct ones).

The product of its digits is 3919104, while the sum is 52.

The square root of 643963867 is about 25376.4431510801. The cubic root of 643963867 is about 863.5493598166.

The spelling of 643963867 in words is "six hundred forty-three million, nine hundred sixty-three thousand, eight hundred sixty-seven".