1666921887824 has 80 divisors (see below), whose sum is σ = 3408601264128. Its totient is φ = 788142047616.

The previous prime is 1666921887797. The next prime is 1666921887859. The reversal of 1666921887824 is 4287881296661.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19132649 + ... + 19219575.

Almost surely, 2^{1666921887824} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1666921887824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1704300632064).

1666921887824 is an abundant number, since it is smaller than the sum of its proper divisors (1741679376304).

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

1666921887824 is a wasteful number, since it uses less digits than its factorization.

1666921887824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87552 (or 87546 counting only the distinct ones).

The product of its digits is 111476736, while the sum is 68.

The spelling of 1666921887824 in words is "one trillion, six hundred sixty-six billion, nine hundred twenty-one million, eight hundred eighty-seven thousand, eight hundred twenty-four".