521433721 has 2 divisors, whose sum is σ = 521433722. Its totient is φ = 521433720.

The previous prime is 521433683. The next prime is 521433763. The reversal of 521433721 is 127334125.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 403407225 + 118026496 = 20085^2 + 10864^2 .

It is a cyclic number.

It is not a de Polignac number, because 521433721 - 2¹⁵ = 521400953 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 521433721.

It is not a weakly prime, because it can be changed into another prime (521433221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260716860 + 260716861.

It is an arithmetic number, because the mean of its divisors is an integer number (260716861).

Almost surely, 2^521433721 is an apocalyptic number.

It is an amenable number.

521433721 is a deficient number, since it is larger than the sum of its proper divisors (1).

521433721 is an equidigital number, since it uses as much as digits as its factorization.

521433721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 28.

The square root of 521433721 is about 22834.9232755444. The cubic root of 521433721 is about 804.8835246781.

Adding to 521433721 its reverse (127334125), we get a palindrome (648767846).

The spelling of 521433721 in words is "five hundred twenty-one million, four hundred thirty-three thousand, seven hundred twenty-one".