661880165 has 8 divisors (see below), whose sum is σ = 809242488. Its totient is φ = 519513280.

The previous prime is 661880119. The next prime is 661880171. The reversal of 661880165 is 561088166.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 283888801 + 377991364 = 16849^2 + 19442^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-661880165 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 1248566 + ... + 1249095.

It is an arithmetic number, because the mean of its divisors is an integer number (101155311).

Almost surely, 2^661880165 is an apocalyptic number.

It is an amenable number.

661880165 is a deficient number, since it is larger than the sum of its proper divisors (147362323).

661880165 is a wasteful number, since it uses less digits than its factorization.

661880165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2497719.

The product of its (nonzero) digits is 69120, while the sum is 41.

The square root of 661880165 is about 25727.0317953704. The cubic root of 661880165 is about 871.4847439443.

The spelling of 661880165 in words is "six hundred sixty-one million, eight hundred eighty thousand, one hundred sixty-five".