778991 has 4 divisors (see below), whose sum is σ = 824832. Its totient is φ = 733152.

The previous prime is 778979. The next prime is 778993. The reversal of 778991 is 199877.

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 778991 - 2⁶ = 778927 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 (778993) 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, 22895 + ... + 22928.

It is an arithmetic number, because the mean of its divisors is an integer number (206208).

2⁷⁷⁸⁹⁹¹ is an apocalyptic number.

778991 is a deficient number, since it is larger than the sum of its proper divisors (45841).

778991 is a wasteful number, since it uses less digits than its factorization.

778991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45840.

The product of its digits is 31752, while the sum is 41.

The square root of 778991 is about 882.6046680139. The cubic root of 778991 is about 92.0119313448.

The spelling of 778991 in words is "seven hundred seventy-eight thousand, nine hundred ninety-one".