643542605 has 4 divisors (see below), whose sum is σ = 772251132. Its totient is φ = 514834080.

The previous prime is 643542593. The next prime is 643542607. The reversal of 643542605 is 506245346.

It is a happy number.

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 151856329 + 491686276 = 12323^2 + 22174^2 .

It is not a de Polignac number, because 643542605 - 2¹² = 643538509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643542607) 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 3 ways as a sum of consecutive naturals, for example, 64354256 + ... + 64354265.

It is an arithmetic number, because the mean of its divisors is an integer number (193062783).

Almost surely, 2^643542605 is an apocalyptic number.

It is an amenable number.

643542605 is a deficient number, since it is larger than the sum of its proper divisors (128708527).

643542605 is a wasteful number, since it uses less digits than its factorization.

643542605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128708526.

The product of its (nonzero) digits is 86400, while the sum is 35.

The square root of 643542605 is about 25368.1415361867. The cubic root of 643542605 is about 863.3610159759.

The spelling of 643542605 in words is "six hundred forty-three million, five hundred forty-two thousand, six hundred five".