521661521 has 8 divisors (see below), whose sum is σ = 539781888. Its totient is φ = 503622000.

The previous prime is 521661499. The next prime is 521661527. The reversal of 521661521 is 125166125.

It is a happy number.

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-521661521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (521661527) 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 7 ways as a sum of consecutive naturals, for example, 6935 + ... + 33036.

It is an arithmetic number, because the mean of its divisors is an integer number (67472736).

Almost surely, 2^521661521 is an apocalyptic number.

It is an amenable number.

521661521 is a deficient number, since it is larger than the sum of its proper divisors (18120367).

521661521 is a wasteful number, since it uses less digits than its factorization.

521661521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40423.

The product of its digits is 3600, while the sum is 29.

The square root of 521661521 is about 22839.9107047291. The cubic root of 521661521 is about 805.0007180787. Note that the first 3 decimals are identical.

The spelling of 521661521 in words is "five hundred twenty-one million, six hundred sixty-one thousand, five hundred twenty-one".