12561721 has 4 divisors (see below), whose sum is σ = 12657744. Its totient is φ = 12465700.

The previous prime is 12561709. The next prime is 12561733. The reversal of 12561721 is 12716521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (12561709) and next prime (12561733).

It is a cyclic number.

It is not a de Polignac number, because 12561721 - 2¹³ = 12553529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12561701) 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, 47815 + ... + 48076.

It is an arithmetic number, because the mean of its divisors is an integer number (3164436).

Almost surely, 2^12561721 is an apocalyptic number.

It is an amenable number.

12561721 is a deficient number, since it is larger than the sum of its proper divisors (96023).

12561721 is an equidigital number, since it uses as much as digits as its factorization.

12561721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96022.

The product of its digits is 840, while the sum is 25.

The square root of 12561721 is about 3544.2518251388. The cubic root of 12561721 is about 232.4607927104.

The spelling of 12561721 in words is "twelve million, five hundred sixty-one thousand, seven hundred twenty-one".