12911821 has 4 divisors (see below), whose sum is σ = 13905052. Its totient is φ = 11918592.

The previous prime is 12911819. The next prime is 12911851. The reversal of 12911821 is 12811921.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12811921 = 727 ⋅17623.

It can be written as a sum of positive squares in 2 ways, for example, as 5546025 + 7365796 = 2355^2 + 2714^2 .

It is a cyclic number.

It is not a de Polignac number, because 12911821 - 2¹ = 12911819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12911851) 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, 496596 + ... + 496621.

It is an arithmetic number, because the mean of its divisors is an integer number (3476263).

Almost surely, 2^12911821 is an apocalyptic number.

It is an amenable number.

12911821 is a deficient number, since it is larger than the sum of its proper divisors (993231).

12911821 is an equidigital number, since it uses as much as digits as its factorization.

12911821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 993230.

The product of its digits is 288, while the sum is 25.

The square root of 12911821 is about 3593.3022416713. The cubic root of 12911821 is about 234.6006254182.

The spelling of 12911821 in words is "twelve million, nine hundred eleven thousand, eight hundred twenty-one".