79278509 has 2 divisors, whose sum is σ = 79278510. Its totient is φ = 79278508.

The previous prime is 79278503. The next prime is 79278523. The reversal of 79278509 is 90587297.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78234025 + 1044484 = 8845^2 + 1022^2 .

It is an emirp because it is prime and its reverse (90587297) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 79278509 - 2²⁰ = 78229933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (79278503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39639254 + 39639255.

It is an arithmetic number, because the mean of its divisors is an integer number (39639255).

Almost surely, 2^79278509 is an apocalyptic number.

It is an amenable number.

79278509 is a deficient number, since it is larger than the sum of its proper divisors (1).

79278509 is an equidigital number, since it uses as much as digits as its factorization.

79278509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 317520, while the sum is 47.

The square root of 79278509 is about 8903.8479883700. The cubic root of 79278509 is about 429.5876866182.

The spelling of 79278509 in words is "seventy-nine million, two hundred seventy-eight thousand, five hundred nine".