6636781 has 2 divisors, whose sum is σ = 6636782. Its totient is φ = 6636780.

The previous prime is 6636779. The next prime is 6636797. The reversal of 6636781 is 1876366.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3861225 + 2775556 = 1965^2 + 1666^2 .

It is a cyclic number.

It is not a de Polignac number, because 6636781 - 2¹ = 6636779 is a prime.

It is a super-2 number, since 2×6636781² = 88093724083922, which contains 22 as substring.

Together with 6636779, it forms a pair of twin primes.

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 6636781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6636701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3318390 + 3318391.

It is an arithmetic number, because the mean of its divisors is an integer number (3318391).

Almost surely, 2^6636781 is an apocalyptic number.

It is an amenable number.

6636781 is a deficient number, since it is larger than the sum of its proper divisors (1).

6636781 is an equidigital number, since it uses as much as digits as its factorization.

6636781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 37.

The square root of 6636781 is about 2576.1950624904. The cubic root of 6636781 is about 187.9255495910.

The spelling of 6636781 in words is "six million, six hundred thirty-six thousand, seven hundred eighty-one".