521333661 has 8 divisors (see below), whose sum is σ = 704633920. Its totient is φ = 342794592.

The previous prime is 521333653. The next prime is 521333671. The reversal of 521333661 is 166333125.

It is a happy number.

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

It is not a de Polignac number, because 521333661 - 2³ = 521333653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521333621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1190041 + ... + 1190478.

It is an arithmetic number, because the mean of its divisors is an integer number (88079240).

Almost surely, 2^521333661 is an apocalyptic number.

It is an amenable number.

521333661 is a deficient number, since it is larger than the sum of its proper divisors (183300259).

521333661 is a wasteful number, since it uses less digits than its factorization.

521333661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2380595.

The product of its digits is 9720, while the sum is 30.

The square root of 521333661 is about 22832.7322280975. The cubic root of 521333661 is about 804.8320372794.

Adding to 521333661 its reverse (166333125), we get a palindrome (687666786).

The spelling of 521333661 in words is "five hundred twenty-one million, three hundred thirty-three thousand, six hundred sixty-one".