20566409 has 2 divisors, whose sum is σ = 20566410. Its totient is φ = 20566408.

The previous prime is 20566391. The next prime is 20566453. The reversal of 20566409 is 90466502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19114384 + 1452025 = 4372^2 + 1205^2 .

It is a cyclic number.

It is not a de Polignac number, because 20566409 - 2²⁴ = 3789193 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20566489) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10283204 + 10283205.

It is an arithmetic number, because the mean of its divisors is an integer number (10283205).

Almost surely, 2^20566409 is an apocalyptic number.

It is an amenable number.

20566409 is a deficient number, since it is larger than the sum of its proper divisors (1).

20566409 is an equidigital number, since it uses as much as digits as its factorization.

20566409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 20566409 is about 4535.0202866139. The cubic root of 20566409 is about 273.9803962390.

The spelling of 20566409 in words is "twenty million, five hundred sixty-six thousand, four hundred nine".