1665840 has 80 divisors (see below), whose sum is σ = 5642496. Its totient is φ = 403200.

The previous prime is 1665827. The next prime is 1665841. The reversal of 1665840 is 485661.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 1665798 and 1665807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2325 + ... + 2955.

2^1665840 is an apocalyptic number.

1665840 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 1665840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2821248).

1665840 is an abundant number, since it is smaller than the sum of its proper divisors (3976656).

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

1665840 is a wasteful number, since it uses less digits than its factorization.

1665840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 658 (or 652 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 1665840 is about 1290.6742424020. The cubic root of 1665840 is about 118.5435044736.

It can be divided in two parts, 166 and 5840, that added together give a palindrome (6006).

The spelling of 1665840 in words is "one million, six hundred sixty-five thousand, eight hundred forty".