78891121 has 4 divisors (see below), whose sum is σ = 78924532. Its totient is φ = 78857712.

The previous prime is 78891119. The next prime is 78891143. The reversal of 78891121 is 12119887.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19678096 + 59213025 = 4436^2 + 7695^2 .

It is a cyclic number.

It is not a de Polignac number, because 78891121 - 2¹ = 78891119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78891161) 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, 12870 + ... + 17983.

It is an arithmetic number, because the mean of its divisors is an integer number (19731133).

Almost surely, 2^78891121 is an apocalyptic number.

It is an amenable number.

78891121 is a deficient number, since it is larger than the sum of its proper divisors (33411).

78891121 is a wasteful number, since it uses less digits than its factorization.

78891121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33410.

The product of its digits is 8064, while the sum is 37.

The square root of 78891121 is about 8882.0673832166. The cubic root of 78891121 is about 428.8868286919.

The spelling of 78891121 in words is "seventy-eight million, eight hundred ninety-one thousand, one hundred twenty-one".