77664221 has 4 divisors (see below), whose sum is σ = 79763292. Its totient is φ = 75565152.

The previous prime is 77664203. The next prime is 77664227. The reversal of 77664221 is 12246677.

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 36844900 + 40819321 = 6070^2 + 6389^2 .

It is a cyclic number.

It is not a de Polignac number, because 77664221 - 2⁶ = 77664157 is a prime.

It is a Duffinian number.

It is a Curzon 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 (77664227) 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, 1049480 + ... + 1049553.

It is an arithmetic number, because the mean of its divisors is an integer number (19940823).

Almost surely, 2^77664221 is an apocalyptic number.

It is an amenable number.

77664221 is a deficient number, since it is larger than the sum of its proper divisors (2099071).

77664221 is a wasteful number, since it uses less digits than its factorization.

77664221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2099070.

The product of its digits is 28224, while the sum is 35.

The square root of 77664221 is about 8812.7306210958. The cubic root of 77664221 is about 426.6518798451.

The spelling of 77664221 in words is "seventy-seven million, six hundred sixty-four thousand, two hundred twenty-one".