20000561 has 4 divisors (see below), whose sum is σ = 22857792. Its totient is φ = 17143332.

The previous prime is 20000543. The next prime is 20000567. The reversal of 20000561 is 16500002.

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 20000561 - 2¹⁰ = 19999537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20000567) 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, 1428605 + ... + 1428618.

It is an arithmetic number, because the mean of its divisors is an integer number (5714448).

Almost surely, 2^20000561 is an apocalyptic number.

It is an amenable number.

20000561 is a deficient number, since it is larger than the sum of its proper divisors (2857231).

20000561 is an equidigital number, since it uses as much as digits as its factorization.

20000561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2857230.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 20000561 is about 4472.1986762665. The cubic root of 20000561 is about 271.4442996162. Note that the first 3 decimals are identical.

Adding to 20000561 its reverse (16500002), we get a palindrome (36500563).

The spelling of 20000561 in words is "twenty million, five hundred sixty-one", and thus it is an aban number.