520165721 has 8 divisors (see below), whose sum is σ = 552646920. Its totient is φ = 488654208.

The previous prime is 520165693. The next prime is 520165753. The reversal of 520165721 is 127561025.

It can be written as a sum of positive squares in 4 ways, for example, as 367297225 + 152868496 = 19165^2 + 12364^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-520165721 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (520105721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 241316 + ... + 243461.

It is an arithmetic number, because the mean of its divisors is an integer number (69080865).

Almost surely, 2^520165721 is an apocalyptic number.

It is an amenable number.

520165721 is a deficient number, since it is larger than the sum of its proper divisors (32481199).

520165721 is a wasteful number, since it uses less digits than its factorization.

520165721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 484843.

The product of its (nonzero) digits is 4200, while the sum is 29.

The square root of 520165721 is about 22807.1418858216. The cubic root of 520165721 is about 804.2305681181.

The spelling of 520165721 in words is "five hundred twenty million, one hundred sixty-five thousand, seven hundred twenty-one".