66844021 has 2 divisors, whose sum is σ = 66844022. Its totient is φ = 66844020.

The previous prime is 66844007. The next prime is 66844067. The reversal of 66844021 is 12044866.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43428100 + 23415921 = 6590^2 + 4839^2 .

It is a cyclic number.

It is not a de Polignac number, because 66844021 - 2⁵ = 66843989 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 (66844321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33422010 + 33422011.

It is an arithmetic number, because the mean of its divisors is an integer number (33422011).

Almost surely, 2^66844021 is an apocalyptic number.

It is an amenable number.

66844021 is a deficient number, since it is larger than the sum of its proper divisors (1).

66844021 is an equidigital number, since it uses as much as digits as its factorization.

66844021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 66844021 is about 8175.8192861633. The cubic root of 66844021 is about 405.8393829470.

Adding to 66844021 its reverse (12044866), we get a palindrome (78888887).

The spelling of 66844021 in words is "sixty-six million, eight hundred forty-four thousand, twenty-one".