66544581 has 4 divisors (see below), whose sum is σ = 88726112. Its totient is φ = 44363052.

The previous prime is 66544561. The next prime is 66544603. The reversal of 66544581 is 18544566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 66544581 - 2⁵ = 66544549 is a prime.

It is a super-2 number, since 2×66544581² = 8856362520931122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66544501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11090761 + ... + 11090766.

It is an arithmetic number, because the mean of its divisors is an integer number (22181528).

Almost surely, 2^66544581 is an apocalyptic number.

It is an amenable number.

66544581 is a deficient number, since it is larger than the sum of its proper divisors (22181531).

66544581 is a wasteful number, since it uses less digits than its factorization.

66544581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22181530.

The product of its digits is 115200, while the sum is 39.

The square root of 66544581 is about 8157.4861936751. The cubic root of 66544581 is about 405.2324652314.

The spelling of 66544581 in words is "sixty-six million, five hundred forty-four thousand, five hundred eighty-one".