660843581 has 2 divisors, whose sum is σ = 660843582. Its totient is φ = 660843580.

The previous prime is 660843563. The next prime is 660843583. The reversal of 660843581 is 185348066.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 350026681 + 310816900 = 18709^2 + 17630^2 .

It is a cyclic number.

It is not a de Polignac number, because 660843581 - 2²⁶ = 593734717 is a prime.

It is a super-2 number, since 2×660843581² = 873428477097807122, which contains 22 as substring.

Together with 660843583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (660843583) 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 as a sum of consecutive naturals, namely, 330421790 + 330421791.

It is an arithmetic number, because the mean of its divisors is an integer number (330421791).

Almost surely, 2^660843581 is an apocalyptic number.

It is an amenable number.

660843581 is a deficient number, since it is larger than the sum of its proper divisors (1).

660843581 is an equidigital number, since it uses as much as digits as its factorization.

660843581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 138240, while the sum is 41.

The square root of 660843581 is about 25706.8780873913. The cubic root of 660843581 is about 871.0295562360.

The spelling of 660843581 in words is "six hundred sixty million, eight hundred forty-three thousand, five hundred eighty-one".