661561166 has 32 divisors (see below), whose sum is σ = 1178634240. Its totient is φ = 272484576.

The previous prime is 661561163. The next prime is 661561217. The reversal of 661561166 is 661165166.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661561163) 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 in 15 ways as a sum of consecutive naturals, for example, 86885 + ... + 94191.

It is an arithmetic number, because the mean of its divisors is an integer number (36832320).

Almost surely, 2^661561166 is an apocalyptic number.

661561166 is a deficient number, since it is larger than the sum of its proper divisors (517073074).

661561166 is a wasteful number, since it uses less digits than its factorization.

661561166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7568.

The product of its digits is 38880, while the sum is 38.

The square root of 661561166 is about 25720.8313629245. The cubic root of 661561166 is about 871.3447148522.

The spelling of 661561166 in words is "six hundred sixty-one million, five hundred sixty-one thousand, one hundred sixty-six".