1665128800 has 72 divisors (see below), whose sum is σ = 4073317416. Its totient is φ = 664688640.

The previous prime is 1665128753. The next prime is 1665128813. The reversal of 1665128800 is 88215661.

It is a self number, because there is not a number n which added to its sum of digits gives 1665128800.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 448552 + ... + 452248.

It is an arithmetic number, because the mean of its divisors is an integer number (56573853).

Almost surely, 2^1665128800 is an apocalyptic number.

1665128800 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 1665128800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2036658708).

1665128800 is an abundant number, since it is smaller than the sum of its proper divisors (2408188616).

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

1665128800 is a wasteful number, since it uses less digits than its factorization.

1665128800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4280 (or 4267 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 37.

The square root of 1665128800 is about 40805.9897564071. The cubic root of 1665128800 is about 1185.2663207669.

It can be divided in two parts, 16651 and 28800, that added together give a triangular number (45451 = T₃₀₁).

The spelling of 1665128800 in words is "one billion, six hundred sixty-five million, one hundred twenty-eight thousand, eight hundred".