78991155 has 12 divisors (see below), whose sum is σ = 136918080. Its totient is φ = 42128592.

The previous prime is 78991153. The next prime is 78991219. The reversal of 78991155 is 55119987.

It is not a de Polignac number, because 78991155 - 2¹ = 78991153 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 1755359 = 78991155 / (7 + 8 + 9 + 9 + 1 + 1 + 5 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 78991155.

It is not an unprimeable number, because it can be changed into a prime (78991153) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 877635 + ... + 877724.

It is an arithmetic number, because the mean of its divisors is an integer number (11409840).

Almost surely, 2^78991155 is an apocalyptic number.

78991155 is a deficient number, since it is larger than the sum of its proper divisors (57926925).

78991155 is a wasteful number, since it uses less digits than its factorization.

78991155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1755370 (or 1755367 counting only the distinct ones).

The product of its digits is 113400, while the sum is 45.

The square root of 78991155 is about 8887.6968332634. The cubic root of 78991155 is about 429.0680283988.

The spelling of 78991155 in words is "seventy-eight million, nine hundred ninety-one thousand, one hundred fifty-five".