1661605 has 8 divisors (see below), whose sum is σ = 2175264. Its totient is φ = 1208400.

The previous prime is 1661599. The next prime is 1661623. The reversal of 1661605 is 5061661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-1661605 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661605.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 15051 + ... + 15160.

It is an arithmetic number, because the mean of its divisors is an integer number (271908).

2^1661605 is an apocalyptic number.

It is an amenable number.

1661605 is a deficient number, since it is larger than the sum of its proper divisors (513659).

1661605 is a wasteful number, since it uses less digits than its factorization.

1661605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30227.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 1661605 is about 1289.0325829862. The cubic root of 1661605 is about 118.4429630500.

It can be divided in two parts, 166 and 1605, that added together give a palindrome (1771).

The spelling of 1661605 in words is "one million, six hundred sixty-one thousand, six hundred five".