12561 has 8 divisors (see below), whose sum is σ = 17280. Its totient is φ = 8112.

The previous prime is 12553. The next prime is 12569. The reversal of 12561 is 16521.

12561 = T₂₈ + T₂₉ + ... + T₄₅.

12561 is a nontrivial binomial coefficient, being equal to C(159, 2).

It is an interprime number because it is at equal distance from previous prime (12553) and next prime (12569).

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

It is not a de Polignac number, because 12561 - 2³ = 12553 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 12561.

It is not an unprimeable number, because it can be changed into a prime (12569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 120 + ... + 198.

It is an arithmetic number, because the mean of its divisors is an integer number (2160).

2¹²⁵⁶¹ is an apocalyptic number.

12561 is the 158-th triangular number.

It is an amenable number.

12561 is a deficient number, since it is larger than the sum of its proper divisors (4719).

12561 is an equidigital number, since it uses as much as digits as its factorization.

12561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135.

The product of its digits is 60, while the sum is 15.

The square root of 12561 is about 112.0758671615. The cubic root of 12561 is about 23.2456345139.

Adding to 12561 its product of digits (60), we get a palindrome (12621).

The spelling of 12561 in words is "twelve thousand, five hundred sixty-one".