66544021 has 2 divisors, whose sum is σ = 66544022. Its totient is φ = 66544020.

The previous prime is 66544013. The next prime is 66544031. The reversal of 66544021 is 12044566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 62583921 + 3960100 = 7911^2 + 1990^2 .

It is a cyclic number.

It is not a de Polignac number, because 66544021 - 2³ = 66544013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66544031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33272010 + 33272011.

It is an arithmetic number, because the mean of its divisors is an integer number (33272011).

Almost surely, 2^66544021 is an apocalyptic number.

It is an amenable number.

66544021 is a deficient number, since it is larger than the sum of its proper divisors (1).

66544021 is an equidigital number, since it uses as much as digits as its factorization.

66544021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 66544021 is about 8157.4518693033. The cubic root of 66544021 is about 405.2313284956.

Adding to 66544021 its reverse (12044566), we get a palindrome (78588587).

The spelling of 66544021 in words is "sixty-six million, five hundred forty-four thousand, twenty-one".