777776221 has 4 divisors (see below), whose sum is σ = 778031100. Its totient is φ = 777521344.

The previous prime is 777776203. The next prime is 777776227. The reversal of 777776221 is 122677777.

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 554602500 + 223173721 = 23550^2 + 14939^2 .

It is a cyclic number.

It is not a de Polignac number, because 777776221 - 2¹⁵ = 777743453 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (777776227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122806 + ... + 128983.

It is an arithmetic number, because the mean of its divisors is an integer number (194507775).

Almost surely, 2^777776221 is an apocalyptic number.

It is an amenable number.

777776221 is a deficient number, since it is larger than the sum of its proper divisors (254879).

777776221 is a wasteful number, since it uses less digits than its factorization.

777776221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254878.

The product of its digits is 403368, while the sum is 46.

The square root of 777776221 is about 27888.6396405418. The cubic root of 777776221 is about 919.6407785507.

The spelling of 777776221 in words is "seven hundred seventy-seven million, seven hundred seventy-six thousand, two hundred twenty-one".