12661561 has 12 divisors (see below), whose sum is σ = 14004900. Its totient is φ = 11438240.

The previous prime is 12661499. The next prime is 12661589. The reversal of 12661561 is 16516621.

It can be written as a sum of positive squares in 2 ways, for example, as 1771561 + 10890000 = 1331^2 + 3300^2 .

It is not a de Polignac number, because 12661561 - 2⁷ = 12661433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12661591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32355 + ... + 32743.

It is an arithmetic number, because the mean of its divisors is an integer number (1167075).

Almost surely, 2^12661561 is an apocalyptic number.

12661561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

12661561 is a deficient number, since it is larger than the sum of its proper divisors (1343339).

12661561 is a wasteful number, since it uses less digits than its factorization.

12661561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 680 (or 669 counting only the distinct ones).

The product of its digits is 2160, while the sum is 28.

The square root of 12661561 is about 3558.3087274715. The cubic root of 12661561 is about 233.0750309422.

The spelling of 12661561 in words is "twelve million, six hundred sixty-one thousand, five hundred sixty-one".