78791809 has 4 divisors (see below), whose sum is σ = 80083540. Its totient is φ = 77500080.

The previous prime is 78791771. The next prime is 78791837. The reversal of 78791809 is 90819787.

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 30558784 + 48233025 = 5528^2 + 6945^2 .

It is a cyclic number.

It is not a de Polignac number, because 78791809 - 2¹⁷ = 78660737 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78791899) 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, 645774 + ... + 645895.

It is an arithmetic number, because the mean of its divisors is an integer number (20020885).

Almost surely, 2^78791809 is an apocalyptic number.

It is an amenable number.

78791809 is a deficient number, since it is larger than the sum of its proper divisors (1291731).

78791809 is a wasteful number, since it uses less digits than its factorization.

78791809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1291730.

The product of its (nonzero) digits is 254016, while the sum is 49.

The square root of 78791809 is about 8876.4750323538. The cubic root of 78791809 is about 428.7067852191.

The spelling of 78791809 in words is "seventy-eight million, seven hundred ninety-one thousand, eight hundred nine".