661645573 has 2 divisors, whose sum is σ = 661645574. Its totient is φ = 661645572.

The previous prime is 661645553. The next prime is 661645597. The reversal of 661645573 is 375546166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 661158369 + 487204 = 25713^2 + 698^2 .

It is a cyclic number.

It is not a de Polignac number, because 661645573 - 2⁵ = 661645541 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661645553) 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, 330822786 + 330822787.

It is an arithmetic number, because the mean of its divisors is an integer number (330822787).

Almost surely, 2^661645573 is an apocalyptic number.

It is an amenable number.

661645573 is a deficient number, since it is larger than the sum of its proper divisors (1).

661645573 is an equidigital number, since it uses as much as digits as its factorization.

661645573 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 453600, while the sum is 43.

The square root of 661645573 is about 25722.4721401346. The cubic root of 661645573 is about 871.3817708693.

The spelling of 661645573 in words is "six hundred sixty-one million, six hundred forty-five thousand, five hundred seventy-three".