643350665 has 4 divisors (see below), whose sum is σ = 772020804. Its totient is φ = 514680528.

The previous prime is 643350647. The next prime is 643350677. The reversal of 643350665 is 566053346.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 566053346 = 2 ⋅283026673.

It can be written as a sum of positive squares in 2 ways, for example, as 373996921 + 269353744 = 19339^2 + 16412^2 .

It is a cyclic number.

It is not a de Polignac number, because 643350665 - 2¹⁶ = 643285129 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64335062 + ... + 64335071.

It is an arithmetic number, because the mean of its divisors is an integer number (193005201).

Almost surely, 2^643350665 is an apocalyptic number.

It is an amenable number.

643350665 is a deficient number, since it is larger than the sum of its proper divisors (128670139).

643350665 is a wasteful number, since it uses less digits than its factorization.

643350665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128670138.

The product of its (nonzero) digits is 194400, while the sum is 38.

The square root of 643350665 is about 25364.3581625871. The cubic root of 643350665 is about 863.2751734381.

The spelling of 643350665 in words is "six hundred forty-three million, three hundred fifty thousand, six hundred sixty-five".