66309581 has 4 divisors (see below), whose sum is σ = 71410332. Its totient is φ = 61208832.

The previous prime is 66309559. The next prime is 66309583. The reversal of 66309581 is 18590366.

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

It can be written as a sum of positive squares in 2 ways, for example, as 37515625 + 28793956 = 6125^2 + 5366^2 .

It is a cyclic number.

It is not a de Polignac number, because 66309581 - 2⁶ = 66309517 is a prime.

It is a super-2 number, since 2×66309581² = 8793921064791122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66309583) 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, 2550356 + ... + 2550381.

It is an arithmetic number, because the mean of its divisors is an integer number (17852583).

Almost surely, 2^66309581 is an apocalyptic number.

It is an amenable number.

66309581 is a deficient number, since it is larger than the sum of its proper divisors (5100751).

66309581 is a wasteful number, since it uses less digits than its factorization.

66309581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5100750.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 66309581 is about 8143.0695072558. The cubic root of 66309581 is about 404.7548808889.

The spelling of 66309581 in words is "sixty-six million, three hundred nine thousand, five hundred eighty-one".