1605509 has 2 divisors, whose sum is σ = 1605510. Its totient is φ = 1605508.

The previous prime is 1605433. The next prime is 1605511. The reversal of 1605509 is 9055061.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1493284 + 112225 = 1222^2 + 335^2 .

It is an emirp because it is prime and its reverse (9055061) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1605509 - 2¹⁶ = 1539973 is a prime.

Together with 1605511, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1605559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 802754 + 802755.

It is an arithmetic number, because the mean of its divisors is an integer number (802755).

2^1605509 is an apocalyptic number.

It is an amenable number.

1605509 is a deficient number, since it is larger than the sum of its proper divisors (1).

1605509 is an equidigital number, since it uses as much as digits as its factorization.

1605509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 1605509 is about 1267.0868162837. The cubic root of 1605509 is about 117.0947925389.

The spelling of 1605509 in words is "one million, six hundred five thousand, five hundred nine".