66543021 has 12 divisors (see below), whose sum is σ = 96651100. Its totient is φ = 44115840.

The previous prime is 66543017. The next prime is 66543031. The reversal of 66543021 is 12034566.

66543021 is a `hidden beast` number, since 6 + 654 + 3 + 0 + 2 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 17388900 + 49154121 = 4170^2 + 7011^2 .

It is not a de Polignac number, because 66543021 - 2² = 66543017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66543011) 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 in 11 ways as a sum of consecutive naturals, for example, 18796 + ... + 22053.

Almost surely, 2^66543021 is an apocalyptic number.

It is an amenable number.

66543021 is a deficient number, since it is larger than the sum of its proper divisors (30108079).

66543021 is a wasteful number, since it uses less digits than its factorization.

66543021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41036 (or 41033 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 66543021 is about 8157.3905754230. The cubic root of 66543021 is about 405.2292985944.

Adding to 66543021 its reverse (12034566), we get a palindrome (78577587).

The spelling of 66543021 in words is "sixty-six million, five hundred forty-three thousand, twenty-one".