66681840 has 80 divisors (see below), whose sum is σ = 208692000. Its totient is φ = 17611776.

The previous prime is 66681829. The next prime is 66681841. The reversal of 66681840 is 4818666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66681841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24886 + ... + 27434.

It is an arithmetic number, because the mean of its divisors is an integer number (2608650).

Almost surely, 2^66681840 is an apocalyptic number.

66681840 is a gapful number since it is divisible by the number (60) 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 66681840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (104346000).

66681840 is an abundant number, since it is smaller than the sum of its proper divisors (142010160).

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

66681840 is a wasteful number, since it uses less digits than its factorization.

66681840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2674 (or 2668 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 39.

The square root of 66681840 is about 8165.8949295224. The cubic root of 66681840 is about 405.5108931308.

The spelling of 66681840 in words is "sixty-six million, six hundred eighty-one thousand, eight hundred forty".