6639891 has 8 divisors (see below), whose sum is σ = 8917440. Its totient is φ = 4394472.

The previous prime is 6639889. The next prime is 6639907. The reversal of 6639891 is 1989366.

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

It is not a de Polignac number, because 6639891 - 2¹ = 6639889 is a prime.

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 7 ways as a sum of consecutive naturals, for example, 7545 + ... + 8378.

It is an arithmetic number, because the mean of its divisors is an integer number (1114680).

Almost surely, 2^6639891 is an apocalyptic number.

6639891 is a deficient number, since it is larger than the sum of its proper divisors (2277549).

6639891 is a wasteful number, since it uses less digits than its factorization.

6639891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16065.

The product of its digits is 69984, while the sum is 42.

The square root of 6639891 is about 2576.7985951564. The cubic root of 6639891 is about 187.9548990197.

The spelling of 6639891 in words is "six million, six hundred thirty-nine thousand, eight hundred ninety-one".