661785173 has 4 divisors (see below), whose sum is σ = 756325920. Its totient is φ = 567244428.

The previous prime is 661785167. The next prime is 661785193. The reversal of 661785173 is 371587166.

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 a cyclic number.

It is not a de Polignac number, because 661785173 - 2⁶ = 661785109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661785193) 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, 47270363 + ... + 47270376.

It is an arithmetic number, because the mean of its divisors is an integer number (189081480).

Almost surely, 2^661785173 is an apocalyptic number.

It is an amenable number.

661785173 is a deficient number, since it is larger than the sum of its proper divisors (94540747).

661785173 is an equidigital number, since it uses as much as digits as its factorization.

661785173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94540746.

The product of its digits is 211680, while the sum is 44.

The square root of 661785173 is about 25725.1855775619. The cubic root of 661785173 is about 871.4430505765.

The spelling of 661785173 in words is "six hundred sixty-one million, seven hundred eighty-five thousand, one hundred seventy-three".