66643641 has 10 divisors (see below), whose sum is σ = 99554202. Its totient is φ = 44429040.

The previous prime is 66643637. The next prime is 66643649. The reversal of 66643641 is 14634666.

It can be written as a sum of positive squares in only one way, i.e., 61168041 + 5475600 = 7821^2 + 2340^2 .

It is not a de Polignac number, because 66643641 - 2² = 66643637 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 66643596 and 66643605.

It is not an unprimeable number, because it can be changed into a prime (66643649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 411300 + ... + 411461.

Almost surely, 2^66643641 is an apocalyptic number.

It is an amenable number.

66643641 is a deficient number, since it is larger than the sum of its proper divisors (32910561).

66643641 is an equidigital number, since it uses as much as digits as its factorization.

66643641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 822773 (or 822764 counting only the distinct ones).

The product of its digits is 62208, while the sum is 36.

The square root of 66643641 is about 8163.5556591476. Note that the first 3 decimals coincide. The cubic root of 66643641 is about 405.4334454108.

The spelling of 66643641 in words is "sixty-six million, six hundred forty-three thousand, six hundred forty-one".