6666417821 has 16 divisors (see below), whose sum is σ = 7715119104. Its totient is φ = 5641887984.

The previous prime is 6666417817. The next prime is 6666417827. The reversal of 6666417821 is 1287146666.

It is a cyclic number.

It is not a de Polignac number, because 6666417821 - 2² = 6666417817 is a prime.

It is a super-2 number, since 2×6666417821² = 88882253128292776082, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6666417827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1838216 + ... + 1841838.

It is an arithmetic number, because the mean of its divisors is an integer number (482194944).

Almost surely, 2^6666417821 is an apocalyptic number.

It is an amenable number.

6666417821 is a deficient number, since it is larger than the sum of its proper divisors (1048701283).

6666417821 is a wasteful number, since it uses less digits than its factorization.

6666417821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6880.

The product of its digits is 580608, while the sum is 47.

The square root of 6666417821 is about 81648.1342162820. The cubic root of 6666417821 is about 1882.0486401969.

The spelling of 6666417821 in words is "six billion, six hundred sixty-six million, four hundred seventeen thousand, eight hundred twenty-one".