1218821 has 2 divisors, whose sum is σ = 1218822. Its totient is φ = 1218820.

The previous prime is 1218787. The next prime is 1218829. The reversal of 1218821 is 1288121.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 748225 + 470596 = 865^2 + 686^2 .

It is a cyclic number.

It is not a de Polignac number, because 1218821 - 2¹⁴ = 1202437 is a prime.

It is a super-3 number, since 3×1218821³ = 5431765845333604983, which contains 333 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1218829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 609410 + 609411.

It is an arithmetic number, because the mean of its divisors is an integer number (609411).

2^1218821 is an apocalyptic number.

It is an amenable number.

1218821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1218821 is an equidigital number, since it uses as much as digits as its factorization.

1218821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 256, while the sum is 23.

The square root of 1218821 is about 1104.0022644904. The cubic root of 1218821 is about 106.8185412501.

The spelling of 1218821 in words is "one million, two hundred eighteen thousand, eight hundred twenty-one".