6639861 has 8 divisors (see below), whose sum is σ = 8974720. Its totient is φ = 4365792.

The previous prime is 6639851. The next prime is 6639863. The reversal of 6639861 is 1689366.

It is a happy number.

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

It is not a de Polignac number, because 6639861 - 2⁹ = 6639349 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6639863) 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, 14941 + ... + 15378.

It is an arithmetic number, because the mean of its divisors is an integer number (1121840).

Almost surely, 2^6639861 is an apocalyptic number.

It is an amenable number.

6639861 is a deficient number, since it is larger than the sum of its proper divisors (2334859).

6639861 is a wasteful number, since it uses less digits than its factorization.

6639861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30395.

The product of its digits is 46656, while the sum is 39.

The square root of 6639861 is about 2576.7927739731. The cubic root of 6639861 is about 187.9546159501.

The spelling of 6639861 in words is "six million, six hundred thirty-nine thousand, eight hundred sixty-one".