644420345 has 4 divisors (see below), whose sum is σ = 773304420. Its totient is φ = 515536272.

The previous prime is 644420327. The next prime is 644420347. The reversal of 644420345 is 543024446.

644420345 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 206899456 + 437520889 = 14384^2 + 20917^2 .

It is a cyclic number.

It is not a de Polignac number, because 644420345 - 2⁸ = 644420089 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644420347) 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, 64442030 + ... + 64442039.

It is an arithmetic number, because the mean of its divisors is an integer number (193326105).

Almost surely, 2^644420345 is an apocalyptic number.

It is an amenable number.

644420345 is a deficient number, since it is larger than the sum of its proper divisors (128884075).

644420345 is a wasteful number, since it uses less digits than its factorization.

644420345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128884074.

The product of its (nonzero) digits is 46080, while the sum is 32.

The square root of 644420345 is about 25385.4356866294. The cubic root of 644420345 is about 863.7533558273.

The spelling of 644420345 in words is "six hundred forty-four million, four hundred twenty thousand, three hundred forty-five".