201666809 has 2 divisors, whose sum is σ = 201666810. Its totient is φ = 201666808.

The previous prime is 201666797. The next prime is 201666827. The reversal of 201666809 is 908666102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 148157584 + 53509225 = 12172^2 + 7315^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-201666809 is a prime.

It is not a weakly prime, because it can be changed into another prime (201666889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 100833404 + 100833405.

It is an arithmetic number, because the mean of its divisors is an integer number (100833405).

Almost surely, 2^201666809 is an apocalyptic number.

It is an amenable number.

201666809 is a deficient number, since it is larger than the sum of its proper divisors (1).

201666809 is an equidigital number, since it uses as much as digits as its factorization.

201666809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 201666809 is about 14200.9439474987. The cubic root of 201666809 is about 586.4236483068.

The spelling of 201666809 in words is "two hundred one million, six hundred sixty-six thousand, eight hundred nine".