1666581728 has 36 divisors (see below), whose sum is σ = 3816773352. Its totient is φ = 714248640.

The previous prime is 1666581727. The next prime is 1666581733. The reversal of 1666581728 is 8271856661.

It is a super-2 number, since 2×1666581728² = 5554989312206931968, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666581727) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 529868 + ... + 533003.

It is an arithmetic number, because the mean of its divisors is an integer number (106021482).

Almost surely, 2^1666581728 is an apocalyptic number.

It is an amenable number.

1666581728 is an abundant number, since it is smaller than the sum of its proper divisors (2150191624).

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

1666581728 is a wasteful number, since it uses less digits than its factorization.

1666581728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1062895 (or 1062880 counting only the distinct ones).

The product of its digits is 967680, while the sum is 50.

The square root of 1666581728 is about 40823.7887511681. The cubic root of 1666581728 is about 1185.6109599695.

The spelling of 1666581728 in words is "one billion, six hundred sixty-six million, five hundred eighty-one thousand, seven hundred twenty-eight".