1665221 has 2 divisors, whose sum is σ = 1665222. Its totient is φ = 1665220.

The previous prime is 1665211. The next prime is 1665233. The reversal of 1665221 is 1225661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1288225 + 376996 = 1135^2 + 614^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665221 - 2¹⁴ = 1648837 is a prime.

It is equal to p₁₂₅₆₉₀ and since 1665221 and 125690 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832610 + 832611.

It is an arithmetic number, because the mean of its divisors is an integer number (832611).

2^1665221 is an apocalyptic number.

It is an amenable number.

1665221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665221 is an equidigital number, since it uses as much as digits as its factorization.

1665221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 23.

The square root of 1665221 is about 1290.4344229755. The cubic root of 1665221 is about 118.5288196860.

The spelling of 1665221 in words is "one million, six hundred sixty-five thousand, two hundred twenty-one".