6658916581 has 4 divisors (see below), whose sum is σ = 6659082252. Its totient is φ = 6658750912.

The previous prime is 6658916549. The next prime is 6658916597. The reversal of 6658916581 is 1856198566.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 3459204225 + 3199712356 = 58815^2 + 56566^2 .

It is a cyclic number.

It is not a de Polignac number, because 6658916581 - 2⁵ = 6658916549 is a prime.

It is a super-2 number, since 2×6658916581² = 88682340065433459122, 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 (6658917581) 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, 20061 + ... + 117133.

It is an arithmetic number, because the mean of its divisors is an integer number (1664770563).

Almost surely, 2^6658916581 is an apocalyptic number.

It is an amenable number.

6658916581 is a deficient number, since it is larger than the sum of its proper divisors (165671).

6658916581 is an equidigital number, since it uses as much as digits as its factorization.

6658916581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165670.

The product of its digits is 3110400, while the sum is 55.

The square root of 6658916581 is about 81602.1849033468. The cubic root of 6658916581 is about 1881.3424639843.

The spelling of 6658916581 in words is "six billion, six hundred fifty-eight million, nine hundred sixteen thousand, five hundred eighty-one".