661543573 has 2 divisors, whose sum is σ = 661543574. Its totient is φ = 661543572.

The previous prime is 661543537. The next prime is 661543583. The reversal of 661543573 is 375345166.

Together with previous prime (661543537) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 425060689 + 236482884 = 20617^2 + 15378^2 .

It is a cyclic number.

It is not a de Polignac number, because 661543573 - 2⁹ = 661543061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661543583) 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, 330771786 + 330771787.

It is an arithmetic number, because the mean of its divisors is an integer number (330771787).

Almost surely, 2^661543573 is an apocalyptic number.

It is an amenable number.

661543573 is a deficient number, since it is larger than the sum of its proper divisors (1).

661543573 is an equidigital number, since it uses as much as digits as its factorization.

661543573 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 226800, while the sum is 40.

The square root of 661543573 is about 25720.4893615965. The cubic root of 661543573 is about 871.3369908481.

The spelling of 661543573 in words is "six hundred sixty-one million, five hundred forty-three thousand, five hundred seventy-three".