16665809 has 2 divisors, whose sum is σ = 16665810. Its totient is φ = 16665808.

The previous prime is 16665769. The next prime is 16665833. The reversal of 16665809 is 90856661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16443025 + 222784 = 4055^2 + 472^2 .

It is a cyclic number.

It is not a de Polignac number, because 16665809 - 2¹² = 16661713 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16665839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8332904 + 8332905.

It is an arithmetic number, because the mean of its divisors is an integer number (8332905).

Almost surely, 2^16665809 is an apocalyptic number.

It is an amenable number.

16665809 is a deficient number, since it is larger than the sum of its proper divisors (1).

16665809 is an equidigital number, since it uses as much as digits as its factorization.

16665809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 77760, while the sum is 41.

The square root of 16665809 is about 4082.3778610021. The cubic root of 16665809 is about 255.4320958023.

The spelling of 16665809 in words is "sixteen million, six hundred sixty-five thousand, eight hundred nine".