640889 has 8 divisors (see below), whose sum is σ = 684000. Its totient is φ = 598752.

The previous prime is 640873. The next prime is 640891. The reversal of 640889 is 988046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640889 - 2⁴ = 640873 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640859) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1502 + ... + 1880.

It is an arithmetic number, because the mean of its divisors is an integer number (85500).

2⁶⁴⁰⁸⁸⁹ is an apocalyptic number.

It is an amenable number.

640889 is a deficient number, since it is larger than the sum of its proper divisors (43111).

640889 is a wasteful number, since it uses less digits than its factorization.

640889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 487.

The product of its (nonzero) digits is 13824, while the sum is 35.

The square root of 640889 is about 800.5554321844. Note that the first 3 decimals coincide. The cubic root of 640889 is about 86.2172710659.

The spelling of 640889 in words is "six hundred forty thousand, eight hundred eighty-nine".