66813840 has 120 divisors (see below), whose sum is σ = 227717568. Its totient is φ = 17552640.

The previous prime is 66813833. The next prime is 66813847. The reversal of 66813840 is 4831866.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (66813833) and next prime (66813847).

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 66813795 and 66813804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66813847) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 50467 + ... + 51773.

Almost surely, 2^66813840 is an apocalyptic number.

66813840 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 66813840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113858784).

66813840 is an abundant number, since it is smaller than the sum of its proper divisors (160903728).

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

66813840 is a wasteful number, since it uses less digits than its factorization.

66813840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1397 (or 1388 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 66813840 is about 8173.9733300274. The cubic root of 66813840 is about 405.7782930536.

The spelling of 66813840 in words is "sixty-six million, eight hundred thirteen thousand, eight hundred forty".