12215821 has 2 divisors, whose sum is σ = 12215822. Its totient is φ = 12215820.

The previous prime is 12215807. The next prime is 12215831. The reversal of 12215821 is 12851221.

12215821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12180100 + 35721 = 3490^2 + 189^2 .

It is a cyclic number.

It is not a de Polignac number, because 12215821 - 2¹⁵ = 12183053 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 12215792 and 12215801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12215831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6107910 + 6107911.

It is an arithmetic number, because the mean of its divisors is an integer number (6107911).

Almost surely, 2^12215821 is an apocalyptic number.

It is an amenable number.

12215821 is a deficient number, since it is larger than the sum of its proper divisors (1).

12215821 is an equidigital number, since it uses as much as digits as its factorization.

12215821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 320, while the sum is 22.

The square root of 12215821 is about 3495.1138751119. The cubic root of 12215821 is about 230.3072202008.

It can be divided in two parts, 12 and 215821, that multiplied together give a palindrome (2589852).

The spelling of 12215821 in words is "twelve million, two hundred fifteen thousand, eight hundred twenty-one".