1666688556 has 96 divisors (see below), whose sum is σ = 4246216128. Its totient is φ = 505774080.

The previous prime is 1666688549. The next prime is 1666688561. The reversal of 1666688556 is 6558866661.

It is a junction number, because it is equal to n+sod(n) for n = 1666688496 and 1666688505.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5931136 + ... + 5931416.

It is an arithmetic number, because the mean of its divisors is an integer number (44231418).

Almost surely, 2^1666688556 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 1666688556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2123108064).

1666688556 is an abundant number, since it is smaller than the sum of its proper divisors (2579527572).

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

1666688556 is a wasteful number, since it uses less digits than its factorization.

1666688556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 691 (or 689 counting only the distinct ones).

The product of its digits is 12441600, while the sum is 57.

The square root of 1666688556 is about 40825.0971339934. The cubic root of 1666688556 is about 1185.6362920088.

The spelling of 1666688556 in words is "one billion, six hundred sixty-six million, six hundred eighty-eight thousand, five hundred fifty-six".