6666561 has 12 divisors (see below), whose sum is σ = 10505040. Its totient is φ = 4040280.

The previous prime is 6666551. The next prime is 6666563. The reversal of 6666561 is 1656666.

It is not a de Polignac number, because 6666561 - 2¹⁰ = 6665537 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (6666563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 33571 + ... + 33768.

It is an arithmetic number, because the mean of its divisors is an integer number (875420).

Almost surely, 2^6666561 is an apocalyptic number.

It is an amenable number.

6666561 is a deficient number, since it is larger than the sum of its proper divisors (3838479).

6666561 is a wasteful number, since it uses less digits than its factorization.

6666561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67356 (or 67353 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 6666561 is about 2581.9684351285. The cubic root of 6666561 is about 188.2062114095.

It can be divided in two parts, 6666 and 561, that added together give a palindrome (7227).

The spelling of 6666561 in words is "six million, six hundred sixty-six thousand, five hundred sixty-one".