78777791 has 4 divisors (see below), whose sum is σ = 78829632. Its totient is φ = 78725952.

The previous prime is 78777703. The next prime is 78777793. The reversal of 78777791 is 19777787.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19777787 = 1747 ⋅11321.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78777791 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 (78777793) 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, 23570 + ... + 26703.

It is an arithmetic number, because the mean of its divisors is an integer number (19707408).

Almost surely, 2^78777791 is an apocalyptic number.

78777791 is a deficient number, since it is larger than the sum of its proper divisors (51841).

78777791 is a wasteful number, since it uses less digits than its factorization.

78777791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51840.

The product of its digits is 1210104, while the sum is 53.

The square root of 78777791 is about 8875.6853819860. The cubic root of 78777791 is about 428.6813596991.

The spelling of 78777791 in words is "seventy-eight million, seven hundred seventy-seven thousand, seven hundred ninety-one".