7878991 has 4 divisors (see below), whose sum is σ = 8133184. Its totient is φ = 7624800.

The previous prime is 7878989. The next prime is 7879021. The reversal of 7878991 is 1998787.

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 7878991 - 2¹ = 7878989 is a prime.

It is a Duffinian number.

7878991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7878911) 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 3 ways as a sum of consecutive naturals, for example, 127050 + ... + 127111.

It is an arithmetic number, because the mean of its divisors is an integer number (2033296).

Almost surely, 2^7878991 is an apocalyptic number.

7878991 is a deficient number, since it is larger than the sum of its proper divisors (254193).

7878991 is a wasteful number, since it uses less digits than its factorization.

7878991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254192.

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

The square root of 7878991 is about 2806.9540430866. The cubic root of 7878991 is about 198.9864640676.

The spelling of 7878991 in words is "seven million, eight hundred seventy-eight thousand, nine hundred ninety-one".