644774777 has 4 divisors (see below), whose sum is σ = 667008420. Its totient is φ = 622541136.

The previous prime is 644774749. The next prime is 644774821. The reversal of 644774777 is 777477446.

It is a happy number.

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 514563856 + 130210921 = 22684^2 + 11411^2 .

It is a cyclic number.

It is not a de Polignac number, because 644774777 - 2¹⁸ = 644512633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644774477) 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, 11116778 + ... + 11116835.

It is an arithmetic number, because the mean of its divisors is an integer number (166752105).

Almost surely, 2^644774777 is an apocalyptic number.

It is an amenable number.

644774777 is a deficient number, since it is larger than the sum of its proper divisors (22233643).

644774777 is a wasteful number, since it uses less digits than its factorization.

644774777 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22233642.

The product of its digits is 6453888, while the sum is 53.

The square root of 644774777 is about 25392.4157377749. The cubic root of 644774777 is about 863.9116819482.

The spelling of 644774777 in words is "six hundred forty-four million, seven hundred seventy-four thousand, seven hundred seventy-seven".