7978891 has 4 divisors (see below), whose sum is σ = 7997752. Its totient is φ = 7960032.

The previous prime is 7978889. The next prime is 7978903. The reversal of 7978891 is 1988797.

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 7978891 - 2¹ = 7978889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7978871) 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, 8781 + ... + 9646.

It is an arithmetic number, because the mean of its divisors is an integer number (1999438).

Almost surely, 2^7978891 is an apocalyptic number.

7978891 is a deficient number, since it is larger than the sum of its proper divisors (18861).

7978891 is a wasteful number, since it uses less digits than its factorization.

7978891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18860.

The product of its digits is 254016, while the sum is 49.

The square root of 7978891 is about 2824.6930806727. The cubic root of 7978891 is about 199.8239367208.

The spelling of 7978891 in words is "seven million, nine hundred seventy-eight thousand, eight hundred ninety-one".