6666788621 has 2 divisors, whose sum is σ = 6666788622. Its totient is φ = 6666788620.

The previous prime is 6666788617. The next prime is 6666788677. The reversal of 6666788621 is 1268876666.

It is a happy number.

It is an a-pointer prime, because the next prime (6666788677) can be obtained adding 6666788621 to its sum of digits (56).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6664273225 + 2515396 = 81635^2 + 1586^2 .

It is a cyclic number.

It is not a de Polignac number, because 6666788621 - 2² = 6666788617 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6666788521) 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 as a sum of consecutive naturals, namely, 3333394310 + 3333394311.

It is an arithmetic number, because the mean of its divisors is an integer number (3333394311).

Almost surely, 2^6666788621 is an apocalyptic number.

It is an amenable number.

6666788621 is a deficient number, since it is larger than the sum of its proper divisors (1).

6666788621 is an equidigital number, since it uses as much as digits as its factorization.

6666788621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6967296, while the sum is 56.

The square root of 6666788621 is about 81650.4049040787. The cubic root of 6666788621 is about 1882.0835340342.

The spelling of 6666788621 in words is "six billion, six hundred sixty-six million, seven hundred eighty-eight thousand, six hundred twenty-one".