643640015 has 4 divisors (see below), whose sum is σ = 772368024. Its totient is φ = 514912008.

The previous prime is 643639993. The next prime is 643640033. The reversal of 643640015 is 510046346.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643640015 - 2¹⁸ = 643377871 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643640015.

It is a congruent number.

It is an unprimeable number.

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, 64363997 + ... + 64364006.

It is an arithmetic number, because the mean of its divisors is an integer number (193092006).

Almost surely, 2^643640015 is an apocalyptic number.

643640015 is a deficient number, since it is larger than the sum of its proper divisors (128728009).

643640015 is a wasteful number, since it uses less digits than its factorization.

643640015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128728008.

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 643640015 is about 25370.0613913329. The cubic root of 643640015 is about 863.4045747359.

The spelling of 643640015 in words is "six hundred forty-three million, six hundred forty thousand, fifteen".