999978779 has 2 divisors, whose sum is σ = 999978780. Its totient is φ = 999978778.

The previous prime is 999978773. The next prime is 999978817. The reversal of 999978779 is 977879999.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 999978779 - 2²⁰ = 998930203 is a prime.

It is not a weakly prime, because it can be changed into another prime (999978773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499989389 + 499989390.

It is an arithmetic number, because the mean of its divisors is an integer number (499989390).

Almost surely, 2^999978779 is an apocalyptic number.

999978779 is a deficient number, since it is larger than the sum of its proper divisors (1).

999978779 is an equidigital number, since it uses as much as digits as its factorization.

999978779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 162030456, while the sum is 74.

The square root of 999978779 is about 31622.4410664326. The cubic root of 999978779 is about 999.9929262833.

The spelling of 999978779 in words is "nine hundred ninety-nine million, nine hundred seventy-eight thousand, seven hundred seventy-nine".