661886665 has 16 divisors (see below), whose sum is σ = 884908800. Its totient is φ = 471128320.

The previous prime is 661886651. The next prime is 661886669. The reversal of 661886665 is 566688166.

It is not a de Polignac number, because 661886665 - 2¹³ = 661878473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661886669) 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 in 15 ways as a sum of consecutive naturals, for example, 125440 + ... + 130609.

It is an arithmetic number, because the mean of its divisors is an integer number (55306800).

Almost surely, 2^661886665 is an apocalyptic number.

It is an amenable number.

661886665 is a deficient number, since it is larger than the sum of its proper divisors (223022135).

661886665 is a wasteful number, since it uses less digits than its factorization.

661886665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256112.

The product of its digits is 2488320, while the sum is 52.

The square root of 661886665 is about 25727.1581213316. The cubic root of 661886665 is about 871.4875967429.

The spelling of 661886665 in words is "six hundred sixty-one million, eight hundred eighty-six thousand, six hundred sixty-five".