1800221 has 2 divisors, whose sum is σ = 1800222. Its totient is φ = 1800220.

The previous prime is 1800209. The next prime is 1800257. The reversal of 1800221 is 1220081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1651225 + 148996 = 1285^2 + 386^2 .

It is a cyclic number.

It is not a de Polignac number, because 1800221 - 2⁶ = 1800157 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1800196 and 1800205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1800121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 900110 + 900111.

It is an arithmetic number, because the mean of its divisors is an integer number (900111).

2^1800221 is an apocalyptic number.

It is an amenable number.

1800221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1800221 is an equidigital number, since it uses as much as digits as its factorization.

1800221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 1800221 is about 1341.7231458091. The cubic root of 1800221 is about 121.6490181027.

Adding to 1800221 its product of nonzero digits (32), we get a triangular number (1800253 = T₁₈₉₇).

The spelling of 1800221 in words is "one million, eight hundred thousand, two hundred twenty-one".