521808121 has 2 divisors, whose sum is σ = 521808122. Its totient is φ = 521808120.

The previous prime is 521808113. The next prime is 521808137. The reversal of 521808121 is 121808125.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 306775225 + 215032896 = 17515^2 + 14664^2 .

It is a cyclic number.

It is not a de Polignac number, because 521808121 - 2³ = 521808113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 521808121.

It is not a weakly prime, because it can be changed into another prime (521800121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260904060 + 260904061.

It is an arithmetic number, because the mean of its divisors is an integer number (260904061).

Almost surely, 2^521808121 is an apocalyptic number.

It is an amenable number.

521808121 is a deficient number, since it is larger than the sum of its proper divisors (1).

521808121 is an equidigital number, since it uses as much as digits as its factorization.

521808121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1280, while the sum is 28.

The square root of 521808121 is about 22843.1197737962. The cubic root of 521808121 is about 805.0761194947.

The spelling of 521808121 in words is "five hundred twenty-one million, eight hundred eight thousand, one hundred twenty-one".