1665820 has 48 divisors (see below), whose sum is σ = 3880800. Its totient is φ = 596736.

The previous prime is 1665767. The next prime is 1665823. The reversal of 1665820 is 285661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665823) 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 15 ways as a sum of consecutive naturals, for example, 11106 + ... + 11254.

It is an arithmetic number, because the mean of its divisors is an integer number (80850).

2^1665820 is an apocalyptic number.

1665820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1665820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1940400).

1665820 is an abundant number, since it is smaller than the sum of its proper divisors (2214980).

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

1665820 is a wasteful number, since it uses less digits than its factorization.

1665820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214 (or 212 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 1665820 is about 1290.6664944903. Note that the first 3 decimals coincide. The cubic root of 1665820 is about 118.5430300624.

It can be divided in two parts, 1665 and 820, that added together give a triangular number (2485 = T₇₀).

The spelling of 1665820 in words is "one million, six hundred sixty-five thousand, eight hundred twenty".