12891821 has 4 divisors (see below), whose sum is σ = 12958812. Its totient is φ = 12824832.

The previous prime is 12891811. The next prime is 12891829. The reversal of 12891821 is 12819821.

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 2937796 + 9954025 = 1714^2 + 3155^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12891821 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12891829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33206 + ... + 33591.

It is an arithmetic number, because the mean of its divisors is an integer number (3239703).

Almost surely, 2^12891821 is an apocalyptic number.

It is an amenable number.

12891821 is a deficient number, since it is larger than the sum of its proper divisors (66991).

12891821 is an equidigital number, since it uses as much as digits as its factorization.

12891821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66990.

The product of its digits is 2304, while the sum is 32.

The square root of 12891821 is about 3590.5182077243. The cubic root of 12891821 is about 234.4794331870.

The spelling of 12891821 in words is "twelve million, eight hundred ninety-one thousand, eight hundred twenty-one".