20205561 has 8 divisors (see below), whose sum is σ = 27449280. Its totient is φ = 13216112.

The previous prime is 20205557. The next prime is 20205587. The reversal of 20205561 is 16550202.

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 20205561 - 2² = 20205557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20205541) 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, 63381 + ... + 63698.

It is an arithmetic number, because the mean of its divisors is an integer number (3431160).

Almost surely, 2^20205561 is an apocalyptic number.

It is an amenable number.

20205561 is a deficient number, since it is larger than the sum of its proper divisors (7243719).

20205561 is a wasteful number, since it uses less digits than its factorization.

20205561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127135.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 20205561 is about 4495.0596214066. The cubic root of 20205561 is about 272.3685576556.

Adding to 20205561 its reverse (16550202), we get a palindrome (36755763).

The spelling of 20205561 in words is "twenty million, two hundred five thousand, five hundred sixty-one".