6644543440 has 20 divisors (see below), whose sum is σ = 15448563684. Its totient is φ = 2657817344.

The previous prime is 6644543431. The next prime is 6644543467. The reversal of 6644543440 is 443454466.

It can be written as a sum of positive squares in 2 ways, for example, as 3160238656 + 3484304784 = 56216^2 + 59028^2 .

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

It is a super-3 number, since 3×6644543440³ (a number of 30 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 6644543393 and 6644543402.

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, 41528317 + ... + 41528476.

Almost surely, 2^6644543440 is an apocalyptic number.

It is an amenable number.

6644543440 is an abundant number, since it is smaller than the sum of its proper divisors (8804020244).

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

6644543440 is a wasteful number, since it uses less digits than its factorization.

6644543440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83056806 (or 83056800 counting only the distinct ones).

The product of its (nonzero) digits is 552960, while the sum is 40.

The square root of 6644543440 is about 81514.0689697184. The cubic root of 6644543440 is about 1879.9878752802.

The spelling of 6644543440 in words is "six billion, six hundred forty-four million, five hundred forty-three thousand, four hundred forty".