66646809 has 12 divisors (see below), whose sum is σ = 96356052. Its totient is φ = 44390400.

The previous prime is 66646787. The next prime is 66646819. The reversal of 66646809 is 90864666.

It can be written as a sum of positive squares in 2 ways, for example, as 29192409 + 37454400 = 5403^2 + 6120^2 .

It is not a de Polignac number, because 66646809 - 2⁹ = 66646297 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66646819) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9529 + ... + 14969.

It is an arithmetic number, because the mean of its divisors is an integer number (8029671).

Almost surely, 2^66646809 is an apocalyptic number.

It is an amenable number.

66646809 is a deficient number, since it is larger than the sum of its proper divisors (29709243).

66646809 is a wasteful number, since it uses less digits than its factorization.

66646809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6808 (or 6805 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 66646809 is about 8163.7496899403. The cubic root of 66646809 is about 405.4398695937.

The spelling of 66646809 in words is "sixty-six million, six hundred forty-six thousand, eight hundred nine".