6399861 has 16 divisors (see below), whose sum is σ = 9253440. Its totient is φ = 3934320.

The previous prime is 6399859. The next prime is 6399889. The reversal of 6399861 is 1689936.

It is not a de Polignac number, because 6399861 - 2¹ = 6399859 is a prime.

It is a Curzon number.

6399861 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6399821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6106 + ... + 7076.

It is an arithmetic number, because the mean of its divisors is an integer number (578340).

Almost surely, 2^6399861 is an apocalyptic number.

It is an amenable number.

6399861 is a deficient number, since it is larger than the sum of its proper divisors (2853579).

6399861 is an equidigital number, since it uses as much as digits as its factorization.

6399861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1013 (or 987 counting only the distinct ones).

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

The square root of 6399861 is about 2529.7946556984. The cubic root of 6399861 is about 185.6622092080.

It can be divided in two parts, 6399 and 861, that added together give a triangular number (7260 = T₁₂₀).

The spelling of 6399861 in words is "six million, three hundred ninety-nine thousand, eight hundred sixty-one".