78978509 has 2 divisors, whose sum is σ = 78978510. Its totient is φ = 78978508.

The previous prime is 78978503. The next prime is 78978541. The reversal of 78978509 is 90587987.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50055625 + 28922884 = 7075^2 + 5378^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78978509 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78978503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39489254 + 39489255.

It is an arithmetic number, because the mean of its divisors is an integer number (39489255).

Almost surely, 2^78978509 is an apocalyptic number.

It is an amenable number.

78978509 is a deficient number, since it is larger than the sum of its proper divisors (1).

78978509 is an equidigital number, since it uses as much as digits as its factorization.

78978509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1270080, while the sum is 53.

The square root of 78978509 is about 8886.9853718795. The cubic root of 78978509 is about 429.0451301225.

The spelling of 78978509 in words is "seventy-eight million, nine hundred seventy-eight thousand, five hundred nine".