644890705 has 8 divisors (see below), whose sum is σ = 774013032. Its totient is φ = 515816448.

The previous prime is 644890703. The next prime is 644890717. The reversal of 644890705 is 507098446.

It can be written as a sum of positive squares in 4 ways, for example, as 95082001 + 549808704 = 9751^2 + 23448^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644890705 - 2¹ = 644890703 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644890703) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32497 + ... + 48433.

It is an arithmetic number, because the mean of its divisors is an integer number (96751629).

Almost surely, 2^644890705 is an apocalyptic number.

It is an amenable number.

644890705 is a deficient number, since it is larger than the sum of its proper divisors (129122327).

644890705 is a wasteful number, since it uses less digits than its factorization.

644890705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24035.

The product of its (nonzero) digits is 241920, while the sum is 43.

The square root of 644890705 is about 25394.6983640287. The cubic root of 644890705 is about 863.9634548336.

The spelling of 644890705 in words is "six hundred forty-four million, eight hundred ninety thousand, seven hundred five".