66171720 has 64 divisors (see below), whose sum is σ = 200376000. Its totient is φ = 17480448.

The previous prime is 66171697. The next prime is 66171739. The reversal of 66171720 is 2717166.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10551 + ... + 15609.

It is an arithmetic number, because the mean of its divisors is an integer number (3130875).

Almost surely, 2^66171720 is an apocalyptic number.

66171720 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 66171720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100188000).

66171720 is an abundant number, since it is smaller than the sum of its proper divisors (134204280).

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

66171720 is a wasteful number, since it uses less digits than its factorization.

66171720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5182 (or 5178 counting only the distinct ones).

The product of its (nonzero) digits is 3528, while the sum is 30.

The square root of 66171720 is about 8134.6001745630. The cubic root of 66171720 is about 404.4741842595.

Adding to 66171720 its reverse (2717166), we get a palindrome (68888886).

The spelling of 66171720 in words is "sixty-six million, one hundred seventy-one thousand, seven hundred twenty".