1666821664 has 24 divisors (see below), whose sum is σ = 3454269840. Its totient is φ = 789546816.

The previous prime is 1666821649. The next prime is 1666821701. The reversal of 1666821664 is 4661286661.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1370134 + ... + 1371349.

It is an arithmetic number, because the mean of its divisors is an integer number (143927910).

Almost surely, 2^1666821664 is an apocalyptic number.

It is an amenable number.

1666821664 is an abundant number, since it is smaller than the sum of its proper divisors (1787448176).

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

1666821664 is a wasteful number, since it uses less digits than its factorization.

1666821664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2741512 (or 2741504 counting only the distinct ones).

The product of its digits is 497664, while the sum is 46.

The square root of 1666821664 is about 40826.7273241439. The cubic root of 1666821664 is about 1185.6678542892.

The spelling of 1666821664 in words is "one billion, six hundred sixty-six million, eight hundred twenty-one thousand, six hundred sixty-four".