78555509 has 2 divisors, whose sum is σ = 78555510. Its totient is φ = 78555508.

The previous prime is 78555479. The next prime is 78555569. The reversal of 78555509 is 90555587.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55726225 + 22829284 = 7465^2 + 4778^2 .

It is an emirp because it is prime and its reverse (90555587) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78555509 - 2¹⁶ = 78489973 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 78555509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78555569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39277754 + 39277755.

It is an arithmetic number, because the mean of its divisors is an integer number (39277755).

Almost surely, 2^78555509 is an apocalyptic number.

It is an amenable number.

78555509 is a deficient number, since it is larger than the sum of its proper divisors (1).

78555509 is an equidigital number, since it uses as much as digits as its factorization.

78555509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 315000, while the sum is 44.

The square root of 78555509 is about 8863.1545738524. The cubic root of 78555509 is about 428.2777860850.

The spelling of 78555509 in words is "seventy-eight million, five hundred fifty-five thousand, five hundred nine".