661560609 has 4 divisors (see below), whose sum is σ = 882080816. Its totient is φ = 441040404.

The previous prime is 661560607. The next prime is 661560623. The reversal of 661560609 is 906065166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 661560609 - 2¹ = 661560607 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661560607) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110260099 + ... + 110260104.

It is an arithmetic number, because the mean of its divisors is an integer number (220520204).

Almost surely, 2^661560609 is an apocalyptic number.

It is an amenable number.

661560609 is a deficient number, since it is larger than the sum of its proper divisors (220520207).

661560609 is a wasteful number, since it uses less digits than its factorization.

661560609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220520206.

The product of its (nonzero) digits is 58320, while the sum is 39.

The square root of 661560609 is about 25720.8205351229. The cubic root of 661560609 is about 871.3444703099.

It can be divided in two parts, 661 and 560609, that added together give a triangular number (561270 = T₁₀₅₉).

The spelling of 661560609 in words is "six hundred sixty-one million, five hundred sixty thousand, six hundred nine".