1666115543400 has 384 divisors, whose sum is σ = 6441723417600. Its totient is φ = 346082457600.

The previous prime is 1666115543381. The next prime is 1666115543401. The reversal of 1666115543400 is 43455116661.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is not an unprimeable number, because it can be changed into a prime (1666115543401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 191217444 + ... + 191226156.

It is an arithmetic number, because the mean of its divisors is an integer number (16775321400).

Almost surely, 2^{1666115543400} is an apocalyptic number.

1666115543400 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 1666115543400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3220861708800).

1666115543400 is an abundant number, since it is smaller than the sum of its proper divisors (4775607874200).

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

1666115543400 is a wasteful number, since it uses less digits than its factorization.

1666115543400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12889 (or 12880 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 42.

The spelling of 1666115543400 in words is "one trillion, six hundred sixty-six billion, one hundred fifteen million, five hundred forty-three thousand, four hundred".