7978391 has 4 divisors (see below), whose sum is σ = 8148192. Its totient is φ = 7808592.

The previous prime is 7978381. The next prime is 7978403. The reversal of 7978391 is 1938797.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7978391 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 (7978301) 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, 84830 + ... + 84923.

It is an arithmetic number, because the mean of its divisors is an integer number (2037048).

Almost surely, 2^7978391 is an apocalyptic number.

7978391 is a deficient number, since it is larger than the sum of its proper divisors (169801).

7978391 is a wasteful number, since it uses less digits than its factorization.

7978391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 169800.

The product of its digits is 95256, while the sum is 44.

The square root of 7978391 is about 2824.6045740953. The cubic root of 7978391 is about 199.8197626212.

The spelling of 7978391 in words is "seven million, nine hundred seventy-eight thousand, three hundred ninety-one".