1666643688 has 384 divisors, whose sum is σ = 5377881600. Its totient is φ = 480743424.

The previous prime is 1666643683. The next prime is 1666643689. The reversal of 1666643688 is 8863466661.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666643683) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 35460481 + ... + 35460527.

It is an arithmetic number, because the mean of its divisors is an integer number (14004900).

Almost surely, 2^1666643688 is an apocalyptic number.

1666643688 is a gapful number since it is divisible by the number (18) 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 1666643688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2688940800).

1666643688 is an abundant number, since it is smaller than the sum of its proper divisors (3711237912).

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

1666643688 is a wasteful number, since it uses less digits than its factorization.

1666643688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 135 counting only the distinct ones).

The product of its digits is 5971968, while the sum is 54.

The square root of 1666643688 is about 40824.5476153747. The cubic root of 1666643688 is about 1185.6256526273.

The spelling of 1666643688 in words is "one billion, six hundred sixty-six million, six hundred forty-three thousand, six hundred eighty-eight".