78917791 has 4 divisors (see below), whose sum is σ = 83560032. Its totient is φ = 74275552.

The previous prime is 78917767. The next prime is 78917801. The reversal of 78917791 is 19771987.

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 78917791 - 2¹¹ = 78915743 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78917711) 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, 2321095 + ... + 2321128.

It is an arithmetic number, because the mean of its divisors is an integer number (20890008).

Almost surely, 2^78917791 is an apocalyptic number.

78917791 is a deficient number, since it is larger than the sum of its proper divisors (4642241).

78917791 is a wasteful number, since it uses less digits than its factorization.

78917791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4642240.

The product of its digits is 222264, while the sum is 49.

The square root of 78917791 is about 8883.5685960092. The cubic root of 78917791 is about 428.9351531965.

The spelling of 78917791 in words is "seventy-eight million, nine hundred seventeen thousand, seven hundred ninety-one".