20132561 has 4 divisors (see below), whose sum is σ = 20279652. Its totient is φ = 19985472.

The previous prime is 20132513. The next prime is 20132569. The reversal of 20132561 is 16523102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16523102 = 2 ⋅8261551.

It can be written as a sum of positive squares in 2 ways, for example, as 4648336 + 15484225 = 2156^2 + 3935^2 .

It is a cyclic number.

It is not a de Polignac number, because 20132561 - 2¹⁴ = 20116177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20132569) 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, 73340 + ... + 73613.

It is an arithmetic number, because the mean of its divisors is an integer number (5069913).

Almost surely, 2^20132561 is an apocalyptic number.

It is an amenable number.

20132561 is a deficient number, since it is larger than the sum of its proper divisors (147091).

20132561 is a wasteful number, since it uses less digits than its factorization.

20132561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147090.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 20132561 is about 4486.9322482070. The cubic root of 20132561 is about 272.0401514041.

Adding to 20132561 its reverse (16523102), we get a palindrome (36655663).

The spelling of 20132561 in words is "twenty million, one hundred thirty-two thousand, five hundred sixty-one".