520721721 has 12 divisors (see below), whose sum is σ = 810011748. Its totient is φ = 320444064.

The previous prime is 520721699. The next prime is 520721723. The reversal of 520721721 is 127127025.

520721721 is a `hidden beast` number, since 520 + 72 + 1 + 72 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 92852496 + 427869225 = 9636^2 + 20685^2 .

It is not a de Polignac number, because 520721721 - 2¹⁵ = 520688953 is a prime.

It is a super-2 number, since 2×520721721² = 542302221442403682, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (520721723) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2225190 + ... + 2225423.

It is an arithmetic number, because the mean of its divisors is an integer number (67500979).

Almost surely, 2^520721721 is an apocalyptic number.

It is an amenable number.

520721721 is a deficient number, since it is larger than the sum of its proper divisors (289290027).

520721721 is a wasteful number, since it uses less digits than its factorization.

520721721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4450632 (or 4450629 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 520721721 is about 22819.3277946569. The cubic root of 520721721 is about 804.5170107866.

Adding to 520721721 its reverse (127127025), we get a palindrome (647848746).

The spelling of 520721721 in words is "five hundred twenty million, seven hundred twenty-one thousand, seven hundred twenty-one".