661544173 has 2 divisors, whose sum is σ = 661544174. Its totient is φ = 661544172.

The previous prime is 661544161. The next prime is 661544197. The reversal of 661544173 is 371445166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 503463844 + 158080329 = 22438^2 + 12573^2 .

It is a cyclic number.

It is not a de Polignac number, because 661544173 - 2¹³ = 661535981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661544153) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330772086 + 330772087.

It is an arithmetic number, because the mean of its divisors is an integer number (330772087).

Almost surely, 2^661544173 is an apocalyptic number.

It is an amenable number.

661544173 is a deficient number, since it is larger than the sum of its proper divisors (1).

661544173 is an equidigital number, since it uses as much as digits as its factorization.

661544173 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 37.

The square root of 661544173 is about 25720.5010254466. The cubic root of 661544173 is about 871.3372542735.

The spelling of 661544173 in words is "six hundred sixty-one million, five hundred forty-four thousand, one hundred seventy-three".