77721856 has 81 divisors (see below), whose sum is σ = 169575861. Its totient is φ = 35546112.

The previous prime is 77721817. The next prime is 77721857. The reversal of 77721856 is 65812777.

The square root of 77721856 is 8816.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 40755456 + 36966400 = 6384^2 + 6080^2 .

It is a Duffinian number.

Its product of digits (164640) is a multiple of the sum of its prime factors (112).

It is not an unprimeable number, because it can be changed into a prime (77721857) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2680050 + ... + 2680078.

Almost surely, 2^77721856 is an apocalyptic number.

77721856 is a gapful number since it is divisible by the number (76) formed by its first and last digit.

77721856 is the 8816-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 77721856

77721856 is an abundant number, since it is smaller than the sum of its proper divisors (91854005).

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

77721856 is an equidigital number, since it uses as much as digits as its factorization.

77721856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112 (or 50 counting only the distinct ones).

The product of its digits is 164640, while the sum is 43.

The cubic root of 77721856 is about 426.7573939007.

The spelling of 77721856 in words is "seventy-seven million, seven hundred twenty-one thousand, eight hundred fifty-six".