78989909 has 2 divisors, whose sum is σ = 78989910. Its totient is φ = 78989908.

The previous prime is 78989893. The next prime is 78989917. The reversal of 78989909 is 90998987.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50367409 + 28622500 = 7097^2 + 5350^2 .

It is an emirp because it is prime and its reverse (90998987) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78989909 - 2⁴ = 78989893 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78989929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39494954 + 39494955.

It is an arithmetic number, because the mean of its divisors is an integer number (39494955).

Almost surely, 2^78989909 is an apocalyptic number.

It is an amenable number.

78989909 is a deficient number, since it is larger than the sum of its proper divisors (1).

78989909 is an equidigital number, since it uses as much as digits as its factorization.

78989909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2939328, while the sum is 59.

The square root of 78989909 is about 8887.6267360865. The cubic root of 78989909 is about 429.0657723590.

The spelling of 78989909 in words is "seventy-eight million, nine hundred eighty-nine thousand, nine hundred nine".