77778649 has 4 divisors (see below), whose sum is σ = 83761636. Its totient is φ = 71795664.

The previous prime is 77778641. The next prime is 77778661. The reversal of 77778649 is 94687777.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 25938649 + 51840000 = 5093^2 + 7200^2 .

It is a cyclic number.

It is not a de Polignac number, because 77778649 - 2³ = 77778641 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 77778649.

It is not an unprimeable number, because it can be changed into a prime (77778641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2991474 + ... + 2991499.

It is an arithmetic number, because the mean of its divisors is an integer number (20940409).

Almost surely, 2^77778649 is an apocalyptic number.

It is an amenable number.

77778649 is a deficient number, since it is larger than the sum of its proper divisors (5982987).

77778649 is a wasteful number, since it uses less digits than its factorization.

77778649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5982986.

The product of its digits is 4148928, while the sum is 55.

The square root of 77778649 is about 8819.2204304009. The cubic root of 77778649 is about 426.8613154694.

The spelling of 77778649 in words is "seventy-seven million, seven hundred seventy-eight thousand, six hundred forty-nine".