20809305 has 64 divisors (see below), whose sum is σ = 41091840. Its totient is φ = 10031040.

The previous prime is 20809303. The next prime is 20809361. The reversal of 20809305 is 50390802.

It is not a de Polignac number, because 20809305 - 2¹ = 20809303 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 120199 + ... + 120371.

It is an arithmetic number, because the mean of its divisors is an integer number (642060).

Almost surely, 2^20809305 is an apocalyptic number.

It is an amenable number.

20809305 is a deficient number, since it is larger than the sum of its proper divisors (20282535).

20809305 is an equidigital number, since it uses as much as digits as its factorization.

20809305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210 (or 192 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 20809305 is about 4561.7217144407. The cubic root of 20809305 is about 275.0547769671.

The spelling of 20809305 in words is "twenty million, eight hundred nine thousand, three hundred five".