66871710821 has 2 divisors, whose sum is σ = 66871710822. Its totient is φ = 66871710820.

The previous prime is 66871710797. The next prime is 66871710839. The reversal of 66871710821 is 12801717866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 57163549921 + 9708160900 = 239089^2 + 98530^2 .

It is a cyclic number.

It is not a de Polignac number, because 66871710821 - 2⁶ = 66871710757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66871715821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33435855410 + 33435855411.

It is an arithmetic number, because the mean of its divisors is an integer number (33435855411).

Almost surely, 2^66871710821 is an apocalyptic number.

It is an amenable number.

66871710821 is a deficient number, since it is larger than the sum of its proper divisors (1).

66871710821 is an equidigital number, since it uses as much as digits as its factorization.

66871710821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 225792, while the sum is 47.

The spelling of 66871710821 in words is "sixty-six billion, eight hundred seventy-one million, seven hundred ten thousand, eight hundred twenty-one".