6646781 has 2 divisors, whose sum is σ = 6646782. Its totient is φ = 6646780.

The previous prime is 6646777. The next prime is 6646819. The reversal of 6646781 is 1876466.

It is an a-pointer prime, because the next prime (6646819) can be obtained adding 6646781 to its sum of digits (38).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6421156 + 225625 = 2534^2 + 475^2 .

It is a cyclic number.

It is not a de Polignac number, because 6646781 - 2² = 6646777 is a prime.

It is a super-2 number, since 2×6646781² = 88359395323922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6643781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3323390 + 3323391.

It is an arithmetic number, because the mean of its divisors is an integer number (3323391).

Almost surely, 2^6646781 is an apocalyptic number.

It is an amenable number.

6646781 is a deficient number, since it is larger than the sum of its proper divisors (1).

6646781 is an equidigital number, since it uses as much as digits as its factorization.

6646781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48384, while the sum is 38.

The square root of 6646781 is about 2578.1351787678. The cubic root of 6646781 is about 188.0198881178.

The spelling of 6646781 in words is "six million, six hundred forty-six thousand, seven hundred eighty-one".