6639859 has 4 divisors (see below), whose sum is σ = 6854080. Its totient is φ = 6425640.

The previous prime is 6639851. The next prime is 6639863. The reversal of 6639859 is 9589366.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9589366 = 2 ⋅4794683.

It is a cyclic number.

It is not a de Polignac number, because 6639859 - 2³ = 6639851 is a prime.

It is a Duffinian number.

6639859 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (6639851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107064 + ... + 107125.

It is an arithmetic number, because the mean of its divisors is an integer number (1713520).

Almost surely, 2^6639859 is an apocalyptic number.

6639859 is a deficient number, since it is larger than the sum of its proper divisors (214221).

6639859 is a wasteful number, since it uses less digits than its factorization.

6639859 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214220.

The product of its digits is 349920, while the sum is 46.

The square root of 6639859 is about 2576.7923858937. The cubic root of 6639859 is about 187.9545970787.

The spelling of 6639859 in words is "six million, six hundred thirty-nine thousand, eight hundred fifty-nine".