640066655 has 16 divisors (see below), whose sum is σ = 807611904. Its totient is φ = 486039840.

The previous prime is 640066649. The next prime is 640066657. The reversal of 640066655 is 556660046.

640066655 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640066655 - 2¹⁰ = 640065631 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 (640066657) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6179 + ... + 36308.

It is an arithmetic number, because the mean of its divisors is an integer number (50475744).

Almost surely, 2^640066655 is an apocalyptic number.

640066655 is a deficient number, since it is larger than the sum of its proper divisors (167545249).

640066655 is a wasteful number, since it uses less digits than its factorization.

640066655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42646.

The product of its (nonzero) digits is 129600, while the sum is 38.

The square root of 640066655 is about 25299.5386321569. The cubic root of 640066655 is about 861.8037924417.

The spelling of 640066655 in words is "six hundred forty million, sixty-six thousand, six hundred fifty-five".