1665720 has 96 divisors (see below), whose sum is σ = 6196320. Its totient is φ = 380160.

The previous prime is 1665709. The next prime is 1665757. The reversal of 1665720 is 275661.

1665720 is a `hidden beast` number, since 1 + 6 + 657 + 2 + 0 = 666.

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 23 ways as a sum of consecutive naturals, for example, 2190 + ... + 2850.

It is an arithmetic number, because the mean of its divisors is an integer number (64545).

2^1665720 is an apocalyptic number.

1665720 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 1665720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3098160).

1665720 is an abundant number, since it is smaller than the sum of its proper divisors (4530600).

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

1665720 is a wasteful number, since it uses less digits than its factorization.

1665720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 685 (or 678 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 1665720 is about 1290.6277542343. The cubic root of 1665720 is about 118.5406579493.

It can be divided in two parts, 166 and 5720, that added together give a triangular number (5886 = T₁₀₈).

The spelling of 1665720 in words is "one million, six hundred sixty-five thousand, seven hundred twenty".