66640820 has 12 divisors (see below), whose sum is σ = 139945764. Its totient is φ = 26656320.

The previous prime is 66640807. The next prime is 66640829. The reversal of 66640820 is 2804666.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 29528356 + 37112464 = 5434^2 + 6092^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66640829) 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 3 ways as a sum of consecutive naturals, for example, 1666001 + ... + 1666040.

It is an arithmetic number, because the mean of its divisors is an integer number (11662147).

Almost surely, 2^66640820 is an apocalyptic number.

It is an amenable number.

66640820 is an abundant number, since it is smaller than the sum of its proper divisors (73304944).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66640820 is a wasteful number, since it uses less digits than its factorization.

66640820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3332050 (or 3332048 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 32.

The square root of 66640820 is about 8163.3828772146. The cubic root of 66640820 is about 405.4277247155.

The spelling of 66640820 in words is "sixty-six million, six hundred forty thousand, eight hundred twenty".