77799991 has 2 divisors, whose sum is σ = 77799992. Its totient is φ = 77799990.

The previous prime is 77799989. The next prime is 77800013. The reversal of 77799991 is 19999777.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 77799991 - 2¹ = 77799989 is a prime.

Together with 77799989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77799901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38899995 + 38899996.

It is an arithmetic number, because the mean of its divisors is an integer number (38899996).

Almost surely, 2^77799991 is an apocalyptic number.

77799991 is a deficient number, since it is larger than the sum of its proper divisors (1).

77799991 is an equidigital number, since it uses as much as digits as its factorization.

77799991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2250423, while the sum is 58.

The square root of 77799991 is about 8820.4303183008. The cubic root of 77799991 is about 426.9003546367.

The spelling of 77799991 in words is "seventy-seven million, seven hundred ninety-nine thousand, nine hundred ninety-one".