6644786681 has 4 divisors (see below), whose sum is σ = 7155924132. Its totient is φ = 6133649232.

The previous prime is 6644786671. The next prime is 6644786683. The reversal of 6644786681 is 1866874466.

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

It can be written as a sum of positive squares in 2 ways, for example, as 788711056 + 5856075625 = 28084^2 + 76525^2 .

It is a cyclic number.

It is not a de Polignac number, because 6644786681 - 2²⁶ = 6577677817 is a prime.

It is a super-2 number, since 2×6644786681² = 88306380071989991522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6644786683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 255568706 + ... + 255568731.

It is an arithmetic number, because the mean of its divisors is an integer number (1788981033).

Almost surely, 2^6644786681 is an apocalyptic number.

It is an amenable number.

6644786681 is a deficient number, since it is larger than the sum of its proper divisors (511137451).

6644786681 is a wasteful number, since it uses less digits than its factorization.

6644786681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 511137450.

The product of its digits is 9289728, while the sum is 56.

The square root of 6644786681 is about 81515.5609745771. The cubic root of 6644786681 is about 1880.0108156349.

The spelling of 6644786681 in words is "six billion, six hundred forty-four million, seven hundred eighty-six thousand, six hundred eighty-one".