20003561 has 4 divisors (see below), whose sum is σ = 21056400. Its totient is φ = 18950724.

The previous prime is 20003549. The next prime is 20003563. The reversal of 20003561 is 16530002.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20003561 - 2⁶ = 20003497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20003563) 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 3 ways as a sum of consecutive naturals, for example, 526391 + ... + 526428.

It is an arithmetic number, because the mean of its divisors is an integer number (5264100).

Almost surely, 2^20003561 is an apocalyptic number.

It is an amenable number.

20003561 is a deficient number, since it is larger than the sum of its proper divisors (1052839).

20003561 is a wasteful number, since it uses less digits than its factorization.

20003561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1052838.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 20003561 is about 4472.5340691827. The cubic root of 20003561 is about 271.4578707720.

Adding to 20003561 its reverse (16530002), we get a palindrome (36533563).

The spelling of 20003561 in words is "twenty million, three thousand, five hundred sixty-one".