21004241521 has 2 divisors, whose sum is σ = 21004241522. Its totient is φ = 21004241520.

The previous prime is 21004241507. The next prime is 21004241537. The reversal of 21004241521 is 12514240012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18520215921 + 2484025600 = 136089^2 + 49840^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004241521 - 2⁷ = 21004241393 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21004241492 and 21004241501.

It is not a weakly prime, because it can be changed into another prime (21004241501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502120760 + 10502120761.

It is an arithmetic number, because the mean of its divisors is an integer number (10502120761).

Almost surely, 2^21004241521 is an apocalyptic number.

It is an amenable number.

21004241521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004241521 is an equidigital number, since it uses as much as digits as its factorization.

21004241521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 640, while the sum is 22.

Adding to 21004241521 its reverse (12514240012), we get a palindrome (33518481533).

The spelling of 21004241521 in words is "twenty-one billion, four million, two hundred forty-one thousand, five hundred twenty-one".