661515173 has 16 divisors (see below), whose sum is σ = 728550720. Its totient is φ = 595660800.

The previous prime is 661515137. The next prime is 661515181. The reversal of 661515173 is 371515166.

It is a cyclic number.

It is not a de Polignac number, because 661515173 - 2¹⁶ = 661449637 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661515133) 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, 595943 + ... + 597051.

It is an arithmetic number, because the mean of its divisors is an integer number (45534420).

Almost surely, 2^661515173 is an apocalyptic number.

It is an amenable number.

661515173 is a deficient number, since it is larger than the sum of its proper divisors (67035547).

661515173 is a wasteful number, since it uses less digits than its factorization.

661515173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1588.

The product of its digits is 18900, while the sum is 35.

The square root of 661515173 is about 25719.9372666420. The cubic root of 661515173 is about 871.3245218662.

The spelling of 661515173 in words is "six hundred sixty-one million, five hundred fifteen thousand, one hundred seventy-three".