643905867 has 16 divisors (see below), whose sum is σ = 966804480. Its totient is φ = 377656800.

The previous prime is 643905863. The next prime is 643905947. The reversal of 643905867 is 768509346.

It is not a de Polignac number, because 643905867 - 2² = 643905863 is a prime.

It is a super-2 number, since 2×643905867² = 829229531114043378, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (643905863) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 313692 + ... + 315737.

It is an arithmetic number, because the mean of its divisors is an integer number (60425280).

Almost surely, 2^643905867 is an apocalyptic number.

643905867 is a deficient number, since it is larger than the sum of its proper divisors (322898613).

643905867 is a wasteful number, since it uses less digits than its factorization.

643905867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 629474.

The product of its (nonzero) digits is 1088640, while the sum is 48.

The square root of 643905867 is about 25375.3003331980. The cubic root of 643905867 is about 863.5234332240.

The spelling of 643905867 in words is "six hundred forty-three million, nine hundred five thousand, eight hundred sixty-seven".