661571609 has 16 divisors (see below), whose sum is σ = 732862080. Its totient is φ = 594021120.

The previous prime is 661571593. The next prime is 661571629. The reversal of 661571609 is 906175166.

661571609 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 661571609 - 2⁴ = 661571593 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (661571629) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 162602 + ... + 166620.

It is an arithmetic number, because the mean of its divisors is an integer number (45803880).

Almost surely, 2^661571609 is an apocalyptic number.

It is an amenable number.

661571609 is a deficient number, since it is larger than the sum of its proper divisors (71290471).

661571609 is a wasteful number, since it uses less digits than its factorization.

661571609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4480.

The product of its (nonzero) digits is 68040, while the sum is 41.

The square root of 661571609 is about 25721.0343687807. The cubic root of 661571609 is about 871.3492996664.

The spelling of 661571609 in words is "six hundred sixty-one million, five hundred seventy-one thousand, six hundred nine".