644662705 has 4 divisors (see below), whose sum is σ = 773595252. Its totient is φ = 515730160.

The previous prime is 644662687. The next prime is 644662717. The reversal of 644662705 is 507266446.

644662705 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 110082064 + 534580641 = 10492^2 + 23121^2 .

It is not a de Polignac number, because 644662705 - 2¹³ = 644654513 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64466266 + ... + 64466275.

It is an arithmetic number, because the mean of its divisors is an integer number (193398813).

Almost surely, 2^644662705 is an apocalyptic number.

It is an amenable number.

644662705 is a deficient number, since it is larger than the sum of its proper divisors (128932547).

644662705 is a wasteful number, since it uses less digits than its factorization.

644662705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128932546.

The product of its (nonzero) digits is 241920, while the sum is 40.

The square root of 644662705 is about 25390.2088412049. The cubic root of 644662705 is about 863.8616252340.

The spelling of 644662705 in words is "six hundred forty-four million, six hundred sixty-two thousand, seven hundred five".