643700605 has 4 divisors (see below), whose sum is σ = 772440732. Its totient is φ = 514960480.

The previous prime is 643700593. The next prime is 643700657. The reversal of 643700605 is 506007346.

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 492262969 + 151437636 = 22187^2 + 12306^2 .

It is not a de Polignac number, because 643700605 - 2²³ = 635311997 is a prime.

It is a Smith number, since the sum of its digits (31) 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 a congruent 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, 64370056 + ... + 64370065.

It is an arithmetic number, because the mean of its divisors is an integer number (193110183).

Almost surely, 2^643700605 is an apocalyptic number.

It is an amenable number.

643700605 is a deficient number, since it is larger than the sum of its proper divisors (128740127).

643700605 is a wasteful number, since it uses less digits than its factorization.

643700605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128740126.

The product of its (nonzero) digits is 15120, while the sum is 31.

The square root of 643700605 is about 25371.2554872635. The cubic root of 643700605 is about 863.4316665059.

The spelling of 643700605 in words is "six hundred forty-three million, seven hundred thousand, six hundred five".