1666686720 has 288 divisors, whose sum is σ = 5637123072. Its totient is φ = 418840576.

The previous prime is 1666686701. The next prime is 1666686739. The reversal of 1666686720 is 276866661.

It is an interprime number because it is at equal distance from previous prime (1666686701) and next prime (1666686739).

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 1666686720.

It is a congruent number.

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, 9980077 + ... + 9980243.

It is an arithmetic number, because the mean of its divisors is an integer number (19573344).

Almost surely, 2^1666686720 is an apocalyptic number.

1666686720 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 1666686720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2818561536).

1666686720 is an abundant number, since it is smaller than the sum of its proper divisors (3970436352).

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

1666686720 is a wasteful number, since it uses less digits than its factorization.

1666686720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327 (or 313 counting only the distinct ones).

The product of its (nonzero) digits is 870912, while the sum is 48.

The square root of 1666686720 is about 40825.0746478191. The cubic root of 1666686720 is about 1185.6358566488.

The spelling of 1666686720 in words is "one billion, six hundred sixty-six million, six hundred eighty-six thousand, seven hundred twenty".