66543221 has 2 divisors, whose sum is σ = 66543222. Its totient is φ = 66543220.

The previous prime is 66543203. The next prime is 66543227. The reversal of 66543221 is 12234566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 42640900 + 23902321 = 6530^2 + 4889^2 .

It is a cyclic number.

It is not a de Polignac number, because 66543221 - 2⁶ = 66543157 is a prime.

It is a super-3 number, since 3×66543221³ (a number of 24 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is equal to p_3926432 and since 66543221 and 3926432 have the same sum of digits, it is a Honaker prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66543227) 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, 33271610 + 33271611.

It is an arithmetic number, because the mean of its divisors is an integer number (33271611).

Almost surely, 2^66543221 is an apocalyptic number.

It is an amenable number.

66543221 is a deficient number, since it is larger than the sum of its proper divisors (1).

66543221 is an equidigital number, since it uses as much as digits as its factorization.

66543221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8640, while the sum is 29.

The square root of 66543221 is about 8157.4028342359. The cubic root of 66543221 is about 405.2297045763.

Adding to 66543221 its reverse (12234566), we get a palindrome (78777787).

The spelling of 66543221 in words is "sixty-six million, five hundred forty-three thousand, two hundred twenty-one".