521661220 has 12 divisors (see below), whose sum is σ = 1095488604. Its totient is φ = 208664480.

The previous prime is 521661197. The next prime is 521661227. The reversal of 521661220 is 22166125.

It can be written as a sum of positive squares in 2 ways, for example, as 116122176 + 405539044 = 10776^2 + 20138^2 .

It is not an unprimeable number, because it can be changed into a prime (521661227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13041511 + ... + 13041550.

It is an arithmetic number, because the mean of its divisors is an integer number (91290717).

Almost surely, 2^521661220 is an apocalyptic number.

It is an amenable number.

521661220 is an abundant number, since it is smaller than the sum of its proper divisors (573827384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

521661220 is a wasteful number, since it uses less digits than its factorization.

521661220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26083070 (or 26083068 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 521661220 is about 22839.9041153854. The cubic root of 521661220 is about 805.0005632495. Note that the first 3 decimals are identical.

The spelling of 521661220 in words is "five hundred twenty-one million, six hundred sixty-one thousand, two hundred twenty".