78945509 has 2 divisors, whose sum is σ = 78945510. Its totient is φ = 78945508.

The previous prime is 78945473. The next prime is 78945521. The reversal of 78945509 is 90554987.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77616100 + 1329409 = 8810^2 + 1153^2 .

It is an emirp because it is prime and its reverse (90554987) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78945509 - 2¹⁶ = 78879973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78948509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39472754 + 39472755.

It is an arithmetic number, because the mean of its divisors is an integer number (39472755).

Almost surely, 2^78945509 is an apocalyptic number.

It is an amenable number.

78945509 is a deficient number, since it is larger than the sum of its proper divisors (1).

78945509 is an equidigital number, since it uses as much as digits as its factorization.

78945509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 453600, while the sum is 47.

The square root of 78945509 is about 8885.1285303028. The cubic root of 78945509 is about 428.9853650805.

The spelling of 78945509 in words is "seventy-eight million, nine hundred forty-five thousand, five hundred nine".