20405543 has 4 divisors (see below), whose sum is σ = 20485200. Its totient is φ = 20325888.

The previous prime is 20405527. The next prime is 20405549. The reversal of 20405543 is 34550402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 34550402 = 2 ⋅17275201.

It is a cyclic number.

It is not a de Polignac number, because 20405543 - 2⁴ = 20405527 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20405549) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39443 + ... + 39956.

It is an arithmetic number, because the mean of its divisors is an integer number (5121300).

Almost surely, 2^20405543 is an apocalyptic number.

20405543 is a deficient number, since it is larger than the sum of its proper divisors (79657).

20405543 is an equidigital number, since it uses as much as digits as its factorization.

20405543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79656.

The product of its (nonzero) digits is 2400, while the sum is 23.

The square root of 20405543 is about 4517.2494949914. The cubic root of 20405543 is about 273.2641871825.

Adding to 20405543 its reverse (34550402), we get a palindrome (54955945).

The spelling of 20405543 in words is "twenty million, four hundred five thousand, five hundred forty-three".