12781521 has 6 divisors (see below), whose sum is σ = 18462210. Its totient is φ = 8521008.

The previous prime is 12781511. The next prime is 12781541. The reversal of 12781521 is 12518721.

It can be written as a sum of positive squares in only one way, i.e., 12173121 + 608400 = 3489^2 + 780^2 .

It is not a de Polignac number, because 12781521 - 2⁹ = 12781009 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12781511) 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 5 ways as a sum of consecutive naturals, for example, 710076 + ... + 710093.

It is an arithmetic number, because the mean of its divisors is an integer number (3077035).

Almost surely, 2^12781521 is an apocalyptic number.

It is an amenable number.

12781521 is a deficient number, since it is larger than the sum of its proper divisors (5680689).

12781521 is a wasteful number, since it uses less digits than its factorization.

12781521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1420175 (or 1420172 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 12781521 is about 3575.1253124891. The cubic root of 12781521 is about 233.8087962516.

The spelling of 12781521 in words is "twelve million, seven hundred eighty-one thousand, five hundred twenty-one".