1666820400 has 480 divisors, whose sum is σ = 6506631168. Its totient is φ = 356659200.

The previous prime is 1666820381. The next prime is 1666820417. The reversal of 1666820400 is 40286661.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 9634714 + ... + 9634886.

Almost surely, 2^1666820400 is an apocalyptic number.

1666820400 is a gapful number since it is divisible by the number (10) 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 1666820400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3253315584).

1666820400 is an abundant number, since it is smaller than the sum of its proper divisors (4839810768).

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

1666820400 is a wasteful number, since it uses less digits than its factorization.

1666820400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269 (or 258 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 33.

The square root of 1666820400 is about 40826.7118440856. The cubic root of 1666820400 is about 1185.6675545802.

The spelling of 1666820400 in words is "one billion, six hundred sixty-six million, eight hundred twenty thousand, four hundred".