1661109 has 4 divisors (see below), whose sum is σ = 2214816. Its totient is φ = 1107404.

The previous prime is 1661069. The next prime is 1661111. The reversal of 1661109 is 9011661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 9011661 = 3 ⋅3003887.

It is a cyclic number.

It is not a de Polignac number, because 1661109 - 2¹² = 1657013 is a prime.

It is a D-number.

It is a Curzon number.

1661109 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661159) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 276849 + ... + 276854.

It is an arithmetic number, because the mean of its divisors is an integer number (553704).

2^1661109 is an apocalyptic number.

It is an amenable number.

1661109 is a deficient number, since it is larger than the sum of its proper divisors (553707).

1661109 is an equidigital number, since it uses as much as digits as its factorization.

1661109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553706.

The product of its (nonzero) digits is 324, while the sum is 24.

The square root of 1661109 is about 1288.8401762825. The cubic root of 1661109 is about 118.4311765432.

It can be divided in two parts, 1661 and 109, that added together give a triangular number (1770 = T₅₉).

The spelling of 1661109 in words is "one million, six hundred sixty-one thousand, one hundred nine".