12321781 has 4 divisors (see below), whose sum is σ = 12746700. Its totient is φ = 11896864.

The previous prime is 12321763. The next prime is 12321797. The reversal of 12321781 is 18712321.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18712321 = 19 ⋅984859.

It can be written as a sum of positive squares in 2 ways, for example, as 6604900 + 5716881 = 2570^2 + 2391^2 .

It is a cyclic number.

It is not a de Polignac number, because 12321781 - 2⁷ = 12321653 is a prime.

It is a super-2 number, since 2×12321781² = 303652574023922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12322781) 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, 212416 + ... + 212473.

It is an arithmetic number, because the mean of its divisors is an integer number (3186675).

Almost surely, 2^12321781 is an apocalyptic number.

It is an amenable number.

12321781 is a deficient number, since it is larger than the sum of its proper divisors (424919).

12321781 is an equidigital number, since it uses as much as digits as its factorization.

12321781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 424918.

The product of its digits is 672, while the sum is 25.

The square root of 12321781 is about 3510.2394505219. The cubic root of 12321781 is about 230.9711988479.

It can be divided in two parts, 123 and 21781, that added together give a square (21904 = 148²).

The spelling of 12321781 in words is "twelve million, three hundred twenty-one thousand, seven hundred eighty-one".