1660405 has 4 divisors (see below), whose sum is σ = 1992492. Its totient is φ = 1328320.

The previous prime is 1660387. The next prime is 1660409. The reversal of 1660405 is 5040661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 956484 + 703921 = 978^2 + 839^2 .

It is not a de Polignac number, because 1660405 - 2⁹ = 1659893 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1660409) 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 3 ways as a sum of consecutive naturals, for example, 166036 + ... + 166045.

It is an arithmetic number, because the mean of its divisors is an integer number (498123).

2^1660405 is an apocalyptic number.

It is an amenable number.

1660405 is a deficient number, since it is larger than the sum of its proper divisors (332087).

1660405 is an equidigital number, since it uses as much as digits as its factorization.

1660405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332086.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 1660405 is about 1288.5670335687. The cubic root of 1660405 is about 118.4144432785.

The spelling of 1660405 in words is "one million, six hundred sixty thousand, four hundred five".