66721171 has 4 divisors (see below), whose sum is σ = 72786744. Its totient is φ = 60655600.

The previous prime is 66721169. The next prime is 66721177. The reversal of 66721171 is 17112766.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 66721171 - 2¹ = 66721169 is a prime.

It is a super-2 number, since 2×66721171² = 8903429319222482, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66721177) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3032770 + ... + 3032791.

It is an arithmetic number, because the mean of its divisors is an integer number (18196686).

Almost surely, 2^66721171 is an apocalyptic number.

66721171 is a deficient number, since it is larger than the sum of its proper divisors (6065573).

66721171 is a wasteful number, since it uses less digits than its factorization.

66721171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6065572.

The product of its digits is 3528, while the sum is 31.

The square root of 66721171 is about 8168.3028224962. The cubic root of 66721171 is about 405.5906050593.

The spelling of 66721171 in words is "sixty-six million, seven hundred twenty-one thousand, one hundred seventy-one".