77856809 has 2 divisors, whose sum is σ = 77856810. Its totient is φ = 77856808.

The previous prime is 77856799. The next prime is 77856829. The reversal of 77856809 is 90865877.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 53699584 + 24157225 = 7328^2 + 4915^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77856809 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (77856829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38928404 + 38928405.

It is an arithmetic number, because the mean of its divisors is an integer number (38928405).

Almost surely, 2^77856809 is an apocalyptic number.

It is an amenable number.

77856809 is a deficient number, since it is larger than the sum of its proper divisors (1).

77856809 is an equidigital number, since it uses as much as digits as its factorization.

77856809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 846720, while the sum is 50.

The square root of 77856809 is about 8823.6505483842. The cubic root of 77856809 is about 427.0042523439.

The spelling of 77856809 in words is "seventy-seven million, eight hundred fifty-six thousand, eight hundred nine".