66108821 has 2 divisors, whose sum is σ = 66108822. Its totient is φ = 66108820.

The previous prime is 66108803. The next prime is 66108829. The reversal of 66108821 is 12880166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 57168721 + 8940100 = 7561^2 + 2990^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66108821 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66108829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33054410 + 33054411.

It is an arithmetic number, because the mean of its divisors is an integer number (33054411).

Almost surely, 2^66108821 is an apocalyptic number.

It is an amenable number.

66108821 is a deficient number, since it is larger than the sum of its proper divisors (1).

66108821 is an equidigital number, since it uses as much as digits as its factorization.

66108821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 66108821 is about 8130.7331157774. The cubic root of 66108821 is about 404.3459870634.

Adding to 66108821 its reverse (12880166), we get a palindrome (78988987).

The spelling of 66108821 in words is "sixty-six million, one hundred eight thousand, eight hundred twenty-one".