643696605 has 32 divisors (see below), whose sum is σ = 1146942720. Its totient is φ = 342527040.

The previous prime is 643696601. The next prime is 643696609. The reversal of 643696605 is 506696346.

643696605 is a `hidden beast` number, since 6 + 4 + 36 + 9 + 6 + 605 = 666.

It is an interprime number because it is at equal distance from previous prime (643696601) and next prime (643696609).

It is not a de Polignac number, because 643696605 - 2² = 643696601 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643696601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 57064 + ... + 67406.

It is an arithmetic number, because the mean of its divisors is an integer number (35841960).

Almost surely, 2^643696605 is an apocalyptic number.

It is an amenable number.

643696605 is a deficient number, since it is larger than the sum of its proper divisors (503246115).

643696605 is a wasteful number, since it uses less digits than its factorization.

643696605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10818 (or 10812 counting only the distinct ones).

The product of its (nonzero) digits is 699840, while the sum is 45.

The square root of 643696605 is about 25371.1766577745. The cubic root of 643696605 is about 863.4298780275.

It can be divided in two parts, 6436 and 96605, that added together give a square (103041 = 321²).

The spelling of 643696605 in words is "six hundred forty-three million, six hundred ninety-six thousand, six hundred five".