6378991 has 4 divisors (see below), whose sum is σ = 6399432. Its totient is φ = 6358552.

The previous prime is 6378989. The next prime is 6379001. The reversal of 6378991 is 1998736.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6378991 - 2¹ = 6378989 is a prime.

It is a Duffinian number.

6378991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6376991) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9745 + ... + 10378.

It is an arithmetic number, because the mean of its divisors is an integer number (1599858).

Almost surely, 2^6378991 is an apocalyptic number.

6378991 is a deficient number, since it is larger than the sum of its proper divisors (20441).

6378991 is a wasteful number, since it uses less digits than its factorization.

6378991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20440.

The product of its digits is 81648, while the sum is 43.

The square root of 6378991 is about 2525.6664467027. Note that the first 3 decimals coincide. The cubic root of 6378991 is about 185.4601740993.

The spelling of 6378991 in words is "six million, three hundred seventy-eight thousand, nine hundred ninety-one".