1661808 has 40 divisors (see below), whose sum is σ = 4352400. Its totient is φ = 546304.

The previous prime is 1661789. The next prime is 1661813. The reversal of 1661808 is 8081661.

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, 4078 + ... + 4466.

It is an arithmetic number, because the mean of its divisors is an integer number (108810).

2^1661808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2176200).

1661808 is an abundant number, since it is smaller than the sum of its proper divisors (2690592).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1661808 is a wasteful number, since it uses less digits than its factorization.

1661808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 489 (or 483 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 1661808 is about 1289.1113218027. Note that the first 3 decimals coincide. The cubic root of 1661808 is about 118.4477862867.

The spelling of 1661808 in words is "one million, six hundred sixty-one thousand, eight hundred eight".