78991105 has 4 divisors (see below), whose sum is σ = 94789332. Its totient is φ = 63192880.

The previous prime is 78991103. The next prime is 78991111. The reversal of 78991105 is 50119987.

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: 50119987 = 2543 ⋅19709.

It can be written as a sum of positive squares in 2 ways, for example, as 48121969 + 30869136 = 6937^2 + 5556^2 .

It is not a de Polignac number, because 78991105 - 2¹ = 78991103 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78991103) 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, 7899106 + ... + 7899115.

It is an arithmetic number, because the mean of its divisors is an integer number (23697333).

Almost surely, 2^78991105 is an apocalyptic number.

It is an amenable number.

78991105 is a deficient number, since it is larger than the sum of its proper divisors (15798227).

78991105 is a wasteful number, since it uses less digits than its factorization.

78991105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15798226.

The product of its (nonzero) digits is 22680, while the sum is 40.

The square root of 78991105 is about 8887.6940203857. The cubic root of 78991105 is about 429.0679378680.

The spelling of 78991105 in words is "seventy-eight million, nine hundred ninety-one thousand, one hundred five".