661605673 has 2 divisors, whose sum is σ = 661605674. Its totient is φ = 661605672.

The previous prime is 661605653. The next prime is 661605691. The reversal of 661605673 is 376506166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 655974544 + 5631129 = 25612^2 + 2373^2 .

It is a cyclic number.

It is not a de Polignac number, because 661605673 - 2⁵ = 661605641 is a prime.

It is not a weakly prime, because it can be changed into another prime (661605653) 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, 330802836 + 330802837.

It is an arithmetic number, because the mean of its divisors is an integer number (330802837).

Almost surely, 2^661605673 is an apocalyptic number.

It is an amenable number.

661605673 is a deficient number, since it is larger than the sum of its proper divisors (1).

661605673 is an equidigital number, since it uses as much as digits as its factorization.

661605673 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 136080, while the sum is 40.

The square root of 661605673 is about 25721.6965420246. The cubic root of 661605673 is about 871.3642545267.

The spelling of 661605673 in words is "six hundred sixty-one million, six hundred five thousand, six hundred seventy-three".