661613321 has 2 divisors, whose sum is σ = 661613322. Its totient is φ = 661613320.

The previous prime is 661613311. The next prime is 661613333. The reversal of 661613321 is 123316166.

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., 579076096 + 82537225 = 24064^2 + 9085^2 .

It is a cyclic number.

It is not a de Polignac number, because 661613321 - 2¹⁰ = 661612297 is a prime.

It is not a weakly prime, because it can be changed into another prime (661613311) 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, 330806660 + 330806661.

It is an arithmetic number, because the mean of its divisors is an integer number (330806661).

Almost surely, 2^661613321 is an apocalyptic number.

It is an amenable number.

661613321 is a deficient number, since it is larger than the sum of its proper divisors (1).

661613321 is an equidigital number, since it uses as much as digits as its factorization.

661613321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 29.

The square root of 661613321 is about 25721.8452098600. The cubic root of 661613321 is about 871.3676120998.

Adding to 661613321 its reverse (123316166), we get a palindrome (784929487).

The spelling of 661613321 in words is "six hundred sixty-one million, six hundred thirteen thousand, three hundred twenty-one".