21200561 has 8 divisors (see below), whose sum is σ = 22360800. Its totient is φ = 20044800.

The previous prime is 21200539. The next prime is 21200563. The reversal of 21200561 is 16500212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21200561 - 2¹⁸ = 20938417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21200563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13886 + ... + 15336.

It is an arithmetic number, because the mean of its divisors is an integer number (2795100).

Almost surely, 2^21200561 is an apocalyptic number.

It is an amenable number.

21200561 is a deficient number, since it is larger than the sum of its proper divisors (1160239).

21200561 is a wasteful number, since it uses less digits than its factorization.

21200561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2239.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21200561 is about 4604.4066935926. The cubic root of 21200561 is about 276.7679419880.

Adding to 21200561 its reverse (16500212), we get a palindrome (37700773).

The spelling of 21200561 in words is "twenty-one million, two hundred thousand, five hundred sixty-one".