1666784640 has 128 divisors (see below), whose sum is σ = 5388145920. Its totient is φ = 438179840.

The previous prime is 1666784617. The next prime is 1666784653. The reversal of 1666784640 is 464876661.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×1666784640² = 5556342072279859200, which contains 22 as substring.

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 1666784640.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 130207 + ... + 142433.

It is an arithmetic number, because the mean of its divisors is an integer number (42094890).

Almost surely, 2^1666784640 is an apocalyptic number.

1666784640 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 1666784640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2694072960).

1666784640 is an abundant number, since it is smaller than the sum of its proper divisors (3721361280).

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

1666784640 is a wasteful number, since it uses less digits than its factorization.

1666784640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12320 (or 12308 counting only the distinct ones).

The product of its (nonzero) digits is 1161216, while the sum is 48.

The square root of 1666784640 is about 40826.2738931684. The cubic root of 1666784640 is about 1185.6590754073.

The spelling of 1666784640 in words is "one billion, six hundred sixty-six million, seven hundred eighty-four thousand, six hundred forty".