20809143 has 10 divisors (see below), whose sum is σ = 31085384. Its totient is φ = 13872708.

The previous prime is 20809141. The next prime is 20809147. The reversal of 20809143 is 34190802.

It is not a de Polignac number, because 20809143 - 2¹ = 20809141 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809141) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 128371 + ... + 128532.

Almost surely, 2^20809143 is an apocalyptic number.

20809143 is a deficient number, since it is larger than the sum of its proper divisors (10276241).

20809143 is an equidigital number, since it uses as much as digits as its factorization.

20809143 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256915 (or 256906 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 20809143 is about 4561.7039579526. The cubic root of 20809143 is about 275.0540632000.

Adding to 20809143 its reverse (34190802), we get a palindrome (54999945).

The spelling of 20809143 in words is "twenty million, eight hundred nine thousand, one hundred forty-three".