1661565 has 8 divisors (see below), whose sum is σ = 2658528. Its totient is φ = 886160.

The previous prime is 1661557. The next prime is 1661567. The reversal of 1661565 is 5651661.

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

It is not a de Polignac number, because 1661565 - 2³ = 1661557 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55371 + ... + 55400.

It is an arithmetic number, because the mean of its divisors is an integer number (332316).

2^1661565 is an apocalyptic number.

1661565 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661565 is a deficient number, since it is larger than the sum of its proper divisors (996963).

1661565 is a wasteful number, since it uses less digits than its factorization.

1661565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110779.

The product of its digits is 5400, while the sum is 30.

The square root of 1661565 is about 1289.0170673812. The cubic root of 1661565 is about 118.4420126122.

The spelling of 1661565 in words is "one million, six hundred sixty-one thousand, five hundred sixty-five".