644768067 has 4 divisors (see below), whose sum is σ = 859690760. Its totient is φ = 429845376.

The previous prime is 644768063. The next prime is 644768081. The reversal of 644768067 is 760867446.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644768067 - 2² = 644768063 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644768063) 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, 107461342 + ... + 107461347.

It is an arithmetic number, because the mean of its divisors is an integer number (214922690).

Almost surely, 2^644768067 is an apocalyptic number.

644768067 is a deficient number, since it is larger than the sum of its proper divisors (214922693).

644768067 is a wasteful number, since it uses less digits than its factorization.

644768067 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214922692.

The product of its (nonzero) digits is 1354752, while the sum is 48.

The square root of 644768067 is about 25392.2836113651. The cubic root of 644768067 is about 863.9086851046.

The spelling of 644768067 in words is "six hundred forty-four million, seven hundred sixty-eight thousand, sixty-seven".