77728909 has 2 divisors, whose sum is σ = 77728910. Its totient is φ = 77728908.

The previous prime is 77728877. The next prime is 77728921. The reversal of 77728909 is 90982777.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 49744809 + 27984100 = 7053^2 + 5290^2 .

It is a cyclic number.

It is not a de Polignac number, because 77728909 - 2⁵ = 77728877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77728949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38864454 + 38864455.

It is an arithmetic number, because the mean of its divisors is an integer number (38864455).

Almost surely, 2^77728909 is an apocalyptic number.

It is an amenable number.

77728909 is a deficient number, since it is larger than the sum of its proper divisors (1).

77728909 is an equidigital number, since it uses as much as digits as its factorization.

77728909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 444528, while the sum is 49.

The square root of 77728909 is about 8816.4000022685. The cubic root of 77728909 is about 426.7703024484.

The spelling of 77728909 in words is "seventy-seven million, seven hundred twenty-eight thousand, nine hundred nine".