20123809 has 2 divisors, whose sum is σ = 20123810. Its totient is φ = 20123808.

The previous prime is 20123783. The next prime is 20123813. The reversal of 20123809 is 90832102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11696400 + 8427409 = 3420^2 + 2903^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20123809 is a prime.

It is not a weakly prime, because it can be changed into another prime (20123899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10061904 + 10061905.

It is an arithmetic number, because the mean of its divisors is an integer number (10061905).

Almost surely, 2^20123809 is an apocalyptic number.

It is an amenable number.

20123809 is a deficient number, since it is larger than the sum of its proper divisors (1).

20123809 is an equidigital number, since it uses as much as digits as its factorization.

20123809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20123809 is about 4485.9568655973. The cubic root of 20123809 is about 272.0007253801. Note that the first 3 decimals are identical.

The spelling of 20123809 in words is "twenty million, one hundred twenty-three thousand, eight hundred nine".