20405603 has 4 divisors (see below), whose sum is σ = 20415360. Its totient is φ = 20395848.

The previous prime is 20405579. The next prime is 20405641. The reversal of 20405603 is 30650402.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 30650402 = 2 ⋅15325201.

It is a cyclic number.

It is not a de Polignac number, because 20405603 - 2¹⁴ = 20389219 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20405663) 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, 323 + ... + 6396.

It is an arithmetic number, because the mean of its divisors is an integer number (5103840).

Almost surely, 2^20405603 is an apocalyptic number.

20405603 is a deficient number, since it is larger than the sum of its proper divisors (9757).

20405603 is an equidigital number, since it uses as much as digits as its factorization.

20405603 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9756.

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 20405603 is about 4517.2561361960. The cubic root of 20405603 is about 273.2644550155.

The spelling of 20405603 in words is "twenty million, four hundred five thousand, six hundred three".