1666213597440 has 1008 divisors, whose sum is σ = 6927472473600. Its totient is φ = 375911497728.

The previous prime is 1666213597423. The next prime is 1666213597441. The reversal of 1666213597440 is 447953126661.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (1008).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (1666213597441) by changing a digit.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 516013746 + ... + 516016974.

Almost surely, 2^{1666213597440} is an apocalyptic number.

1666213597440 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 1666213597440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3463736236800).

1666213597440 is an abundant number, since it is smaller than the sum of its proper divisors (5261258876160).

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

1666213597440 is an frugal number, since it uses more digits than its factorization.

1666213597440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3354 (or 3325 counting only the distinct ones).

The product of its (nonzero) digits is 6531840, while the sum is 54.

The spelling of 1666213597440 in words is "one trillion, six hundred sixty-six billion, two hundred thirteen million, five hundred ninety-seven thousand, four hundred forty".