77666778 has 96 divisors (see below), whose sum is σ = 206219520. Its totient is φ = 20620800.

The previous prime is 77666773. The next prime is 77666789. The reversal of 77666778 is 87766677.

It is a happy number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (77666773) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 216163 + ... + 216521.

It is an arithmetic number, because the mean of its divisors is an integer number (2148120).

Almost surely, 2^77666778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 77666778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103109760).

77666778 is an abundant number, since it is smaller than the sum of its proper divisors (128552742).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

77666778 is a wasteful number, since it uses less digits than its factorization.

77666778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 492 (or 489 counting only the distinct ones).

The product of its digits is 4148928, while the sum is 54.

The square root of 77666778 is about 8812.8756941194. The cubic root of 77666778 is about 426.6565621251.

The spelling of 77666778 in words is "seventy-seven million, six hundred sixty-six thousand, seven hundred seventy-eight".