6398991 has 24 divisors (see below), whose sum is σ = 10158720. Its totient is φ = 3863376.

The previous prime is 6398983. The next prime is 6398999. The reversal of 6398991 is 1998936.

6398991 is a `hidden beast` number, since 639 + 8 + 9 + 9 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (6398983) and next prime (6398999).

It is not a de Polignac number, because 6398991 - 2³ = 6398983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6398999) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3120 + ... + 4746.

It is an arithmetic number, because the mean of its divisors is an integer number (423280).

Almost surely, 2^6398991 is an apocalyptic number.

6398991 is a deficient number, since it is larger than the sum of its proper divisors (3759729).

6398991 is a wasteful number, since it uses less digits than its factorization.

6398991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1675 (or 1672 counting only the distinct ones).

The product of its digits is 104976, while the sum is 45.

The square root of 6398991 is about 2529.6226991391. The cubic root of 6398991 is about 185.6537958252.

The spelling of 6398991 in words is "six million, three hundred ninety-eight thousand, nine hundred ninety-one".