6643861 has 6 divisors (see below), whose sum is σ = 7728630. Its totient is φ = 5694696.

The previous prime is 6643859. The next prime is 6643883. The reversal of 6643861 is 1683466.

It can be written as a sum of positive squares in only one way, i.e., 6599761 + 44100 = 2569^2 + 210^2 .

It is not a de Polignac number, because 6643861 - 2¹ = 6643859 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6643811) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 67746 + ... + 67843.

It is an arithmetic number, because the mean of its divisors is an integer number (1288105).

Almost surely, 2^6643861 is an apocalyptic number.

It is an amenable number.

6643861 is a deficient number, since it is larger than the sum of its proper divisors (1084769).

6643861 is a wasteful number, since it uses less digits than its factorization.

6643861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135603 (or 135596 counting only the distinct ones).

The product of its digits is 20736, while the sum is 34.

The square root of 6643861 is about 2577.5688157642. The cubic root of 6643861 is about 187.9923510544.

The spelling of 6643861 in words is "six million, six hundred forty-three thousand, eight hundred sixty-one".