661622173 has 4 divisors (see below), whose sum is σ = 669056220. Its totient is φ = 654188128.

The previous prime is 661622113. The next prime is 661622177. The reversal of 661622173 is 371226166.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 371226166 = 2 ⋅185613083.

It can be written as a sum of positive squares in 2 ways, for example, as 39967684 + 621654489 = 6322^2 + 24933^2 .

It is a cyclic number.

It is not a de Polignac number, because 661622173 - 2⁹ = 661621661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661622177) 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 3 ways as a sum of consecutive naturals, for example, 3716890 + ... + 3717067.

It is an arithmetic number, because the mean of its divisors is an integer number (167264055).

Almost surely, 2^661622173 is an apocalyptic number.

It is an amenable number.

661622173 is a deficient number, since it is larger than the sum of its proper divisors (7434047).

661622173 is an equidigital number, since it uses as much as digits as its factorization.

661622173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7434046.

The product of its digits is 18144, while the sum is 34.

The square root of 661622173 is about 25722.0172809210. The cubic root of 661622173 is about 871.3714982125.

The spelling of 661622173 in words is "six hundred sixty-one million, six hundred twenty-two thousand, one hundred seventy-three".