1878221 has 2 divisors, whose sum is σ = 1878222. Its totient is φ = 1878220.

The previous prime is 1878209. The next prime is 1878223. The reversal of 1878221 is 1228781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1729225 + 148996 = 1315^2 + 386^2 .

It is a cyclic number.

It is not a de Polignac number, because 1878221 - 2¹⁸ = 1616077 is a prime.

It is a Sophie Germain prime.

Together with 1878223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1878223) 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 as a sum of consecutive naturals, namely, 939110 + 939111.

It is an arithmetic number, because the mean of its divisors is an integer number (939111).

2^1878221 is an apocalyptic number.

It is an amenable number.

1878221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1878221 is an equidigital number, since it uses as much as digits as its factorization.

1878221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1792, while the sum is 29.

The square root of 1878221 is about 1370.4820319873. The cubic root of 1878221 is about 123.3811737139.

The spelling of 1878221 in words is "one million, eight hundred seventy-eight thousand, two hundred twenty-one".