1665421 has 2 divisors, whose sum is σ = 1665422. Its totient is φ = 1665420.

The previous prime is 1665343. The next prime is 1665427. The reversal of 1665421 is 1245661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1155625 + 509796 = 1075^2 + 714^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665421 - 2⁹ = 1664909 is a prime.

1665421 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832710 + 832711.

It is an arithmetic number, because the mean of its divisors is an integer number (832711).

2^1665421 is an apocalyptic number.

It is an amenable number.

1665421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665421 is an equidigital number, since it uses as much as digits as its factorization.

1665421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 25.

The square root of 1665421 is about 1290.5119139318. The cubic root of 1665421 is about 118.5335647649.

The spelling of 1665421 in words is "one million, six hundred sixty-five thousand, four hundred twenty-one".