643887 has 12 divisors (see below), whose sum is σ = 962520. Its totient is φ = 414288.

The previous prime is 643883. The next prime is 643889. The reversal of 643887 is 788346.

643887 is a `hidden beast` number, since 643 + 8 + 8 + 7 = 666.

643887 is nontrivially palindromic in base 15.

It is not a de Polignac number, because 643887 - 2² = 643883 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643883) 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, 973 + ... + 1494.

It is an arithmetic number, because the mean of its divisors is an integer number (80210).

2⁶⁴³⁸⁸⁷ is an apocalyptic number.

643887 is a deficient number, since it is larger than the sum of its proper divisors (318633).

643887 is a wasteful number, since it uses less digits than its factorization.

643887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2502 (or 2499 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 643887 is about 802.4256974948. The cubic root of 643887 is about 86.3514999147.

The spelling of 643887 in words is "six hundred forty-three thousand, eight hundred eighty-seven".