643870 has 24 divisors (see below), whose sum is σ = 1215432. Its totient is φ = 245520.

The previous prime is 643859. The next prime is 643873. The reversal of 643870 is 78346.

It is a Smith number, since the sum of its digits (28) 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 (643873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9577 + ... + 9643.

It is an arithmetic number, because the mean of its divisors is an integer number (50643).

2⁶⁴³⁸⁷⁰ is an apocalyptic number.

643870 is a deficient number, since it is larger than the sum of its proper divisors (571562).

643870 is a wasteful number, since it uses less digits than its factorization.

643870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136 (or 105 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 643870 is about 802.4151045438. The cubic root of 643870 is about 86.3507399529.

The spelling of 643870 in words is "six hundred forty-three thousand, eight hundred seventy".