20201561 has 4 divisors (see below), whose sum is σ = 20694324. Its totient is φ = 19708800.

The previous prime is 20201557. The next prime is 20201563. The reversal of 20201561 is 16510202.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5494336 + 14707225 = 2344^2 + 3835^2 .

It is a cyclic number.

It is not a de Polignac number, because 20201561 - 2² = 20201557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20201563) 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, 246320 + ... + 246401.

It is an arithmetic number, because the mean of its divisors is an integer number (5173581).

Almost surely, 2^20201561 is an apocalyptic number.

It is an amenable number.

20201561 is a deficient number, since it is larger than the sum of its proper divisors (492763).

20201561 is an equidigital number, since it uses as much as digits as its factorization.

20201561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 492762.

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

The square root of 20201561 is about 4494.6146664647. The cubic root of 20201561 is about 272.3505832948.

Adding to 20201561 its reverse (16510202), we get a palindrome (36711763).

The spelling of 20201561 in words is "twenty million, two hundred one thousand, five hundred sixty-one".