20043561 has 16 divisors (see below), whose sum is σ = 28569024. Its totient is φ = 12455424.

The previous prime is 20043559. The next prime is 20043571. The reversal of 20043561 is 16534002.

20043561 = T₁₉₈ + T₁₉₉ + ... + T₅₀₃.

It is a happy number.

It is not a de Polignac number, because 20043561 - 2¹ = 20043559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20043571) 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 15 ways as a sum of consecutive naturals, for example, 3621 + ... + 7293.

It is an arithmetic number, because the mean of its divisors is an integer number (1785564).

Almost surely, 2^20043561 is an apocalyptic number.

It is an amenable number.

20043561 is a deficient number, since it is larger than the sum of its proper divisors (8525463).

20043561 is a wasteful number, since it uses less digits than its factorization.

20043561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3800.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 20043561 is about 4477.0035738203. The cubic root of 20043561 is about 271.6386899984.

Adding to 20043561 its reverse (16534002), we get a palindrome (36577563).

It can be divided in two parts, 2004 and 3561, that added together give a triangular number (5565 = T₁₀₅).

The spelling of 20043561 in words is "twenty million, forty-three thousand, five hundred sixty-one".