643606655 has 16 divisors (see below), whose sum is σ = 844141824. Its totient is φ = 468963840.

The previous prime is 643606637. The next prime is 643606709. The reversal of 643606655 is 556606346.

It is a happy number.

643606655 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 643606655 - 2⁶ = 643606591 is a prime.

It is a Duffinian number.

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 15 ways as a sum of consecutive naturals, for example, 119492 + ... + 124761.

It is an arithmetic number, because the mean of its divisors is an integer number (52758864).

Almost surely, 2^643606655 is an apocalyptic number.

643606655 is a deficient number, since it is larger than the sum of its proper divisors (200535169).

643606655 is a wasteful number, since it uses less digits than its factorization.

643606655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 244306.

The product of its (nonzero) digits is 388800, while the sum is 41.

The square root of 643606655 is about 25369.4039149524. The cubic root of 643606655 is about 863.3896576634.

The spelling of 643606655 in words is "six hundred forty-three million, six hundred six thousand, six hundred fifty-five".