661328189 has 2 divisors, whose sum is σ = 661328190. Its totient is φ = 661328188.

The previous prime is 661328167. The next prime is 661328191. The reversal of 661328189 is 981823166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 397005625 + 264322564 = 19925^2 + 16258^2 .

It is a cyclic number.

It is not a de Polignac number, because 661328189 - 2²⁸ = 392892733 is a prime.

Together with 661328191, 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 (661328489) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330664094 + 330664095.

It is an arithmetic number, because the mean of its divisors is an integer number (330664095).

Almost surely, 2^661328189 is an apocalyptic number.

It is an amenable number.

661328189 is a deficient number, since it is larger than the sum of its proper divisors (1).

661328189 is an equidigital number, since it uses as much as digits as its factorization.

661328189 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 44.

The square root of 661328189 is about 25716.3020086481. The cubic root of 661328189 is about 871.2424178802.

The spelling of 661328189 in words is "six hundred sixty-one million, three hundred twenty-eight thousand, one hundred eighty-nine".