661505641 has 2 divisors, whose sum is σ = 661505642. Its totient is φ = 661505640.

The previous prime is 661505629. The next prime is 661505657. The reversal of 661505641 is 146505166.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 372335616 + 289170025 = 19296^2 + 17005^2 .

It is a cyclic number.

It is not a de Polignac number, because 661505641 - 2⁵ = 661505609 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 661505597 and 661505606.

It is not a weakly prime, because it can be changed into another prime (661505681) 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, 330752820 + 330752821.

It is an arithmetic number, because the mean of its divisors is an integer number (330752821).

Almost surely, 2^661505641 is an apocalyptic number.

It is an amenable number.

661505641 is a deficient number, since it is larger than the sum of its proper divisors (1).

661505641 is an equidigital number, since it uses as much as digits as its factorization.

661505641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 661505641 is about 25719.7519622566. The cubic root of 661505641 is about 871.3203367743.

The spelling of 661505641 in words is "six hundred sixty-one million, five hundred five thousand, six hundred forty-one".