6436640720 has 20 divisors (see below), whose sum is σ = 14965189860. Its totient is φ = 2574656256.

The previous prime is 6436640713. The next prime is 6436640767. The reversal of 6436640720 is 270466346.

It can be written as a sum of positive squares in 2 ways, for example, as 1272206224 + 5164434496 = 35668^2 + 71864^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40228925 + ... + 40229084.

It is an arithmetic number, because the mean of its divisors is an integer number (748259493).

Almost surely, 2^6436640720 is an apocalyptic number.

It is an amenable number.

6436640720 is an abundant number, since it is smaller than the sum of its proper divisors (8528549140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6436640720 is a wasteful number, since it uses less digits than its factorization.

6436640720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80458022 (or 80458016 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 38.

The square root of 6436640720 is about 80228.6776657823. The cubic root of 6436640720 is about 1860.1719423273.

The spelling of 6436640720 in words is "six billion, four hundred thirty-six million, six hundred forty thousand, seven hundred twenty".