66820009 has 2 divisors, whose sum is σ = 66820010. Its totient is φ = 66820008.

The previous prime is 66820007. The next prime is 66820027. The reversal of 66820009 is 90002866.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55830784 + 10989225 = 7472^2 + 3315^2 .

It is a cyclic number.

It is not a de Polignac number, because 66820009 - 2¹ = 66820007 is a prime.

Together with 66820007, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (66820003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33410004 + 33410005.

It is an arithmetic number, because the mean of its divisors is an integer number (33410005).

Almost surely, 2^66820009 is an apocalyptic number.

It is an amenable number.

66820009 is a deficient number, since it is larger than the sum of its proper divisors (1).

66820009 is an equidigital number, since it uses as much as digits as its factorization.

66820009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 66820009 is about 8174.3506775768. The cubic root of 66820009 is about 405.7907813308.

The spelling of 66820009 in words is "sixty-six million, eight hundred twenty thousand, nine".