78779009 has 2 divisors, whose sum is σ = 78779010. Its totient is φ = 78779008.

The previous prime is 78778991. The next prime is 78779011. The reversal of 78779009 is 90097787.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62457409 + 16321600 = 7903^2 + 4040^2 .

It is a cyclic number.

It is not a de Polignac number, because 78779009 - 2¹⁶ = 78713473 is a prime.

It is a super-2 number, since 2×78779009² = 12412264518044162, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 78779011, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (78779039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39389504 + 39389505.

It is an arithmetic number, because the mean of its divisors is an integer number (39389505).

Almost surely, 2^78779009 is an apocalyptic number.

It is an amenable number.

78779009 is a deficient number, since it is larger than the sum of its proper divisors (1).

78779009 is an equidigital number, since it uses as much as digits as its factorization.

78779009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 222264, while the sum is 47.

The square root of 78779009 is about 8875.7539961403. The cubic root of 78779009 is about 428.6835689986.

The spelling of 78779009 in words is "seventy-eight million, seven hundred seventy-nine thousand, nine".