665561305 has 16 divisors (see below), whose sum is σ = 846388224. Its totient is φ = 500693760.

The previous prime is 665561287. The next prime is 665561321. The reversal of 665561305 is 503165566.

It is a happy number.

It is not a de Polignac number, because 665561305 - 2¹³ = 665553113 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 122374 + ... + 127696.

It is an arithmetic number, because the mean of its divisors is an integer number (52899264).

Almost surely, 2^665561305 is an apocalyptic number.

It is an amenable number.

665561305 is a deficient number, since it is larger than the sum of its proper divisors (180826919).

665561305 is a wasteful number, since it uses less digits than its factorization.

665561305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6816.

The product of its (nonzero) digits is 81000, while the sum is 37.

The square root of 665561305 is about 25798.4748580221. The cubic root of 665561305 is about 873.0973864705.

The spelling of 665561305 in words is "six hundred sixty-five million, five hundred sixty-one thousand, three hundred five".