6407991 has 10 divisors (see below), whose sum is σ = 9572552. Its totient is φ = 4271940.

The previous prime is 6407981. The next prime is 6408023. The reversal of 6407991 is 1997046.

6407991 is a `hidden beast` number, since 640 + 7 + 9 + 9 + 1 = 666.

It is not a de Polignac number, because 6407991 - 2¹¹ = 6405943 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 (6407941) 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 9 ways as a sum of consecutive naturals, for example, 39475 + ... + 39636.

Almost surely, 2^6407991 is an apocalyptic number.

6407991 is a deficient number, since it is larger than the sum of its proper divisors (3164561).

6407991 is an equidigital number, since it uses as much as digits as its factorization.

6407991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79123 (or 79114 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 36.

The square root of 6407991 is about 2531.4009954964. The cubic root of 6407991 is about 185.7407939901.

The spelling of 6407991 in words is "six million, four hundred seven thousand, nine hundred ninety-one".