21515523404021 has 2 divisors, whose sum is σ = 21515523404022. Its totient is φ = 21515523404020.

The previous prime is 21515523403991. The next prime is 21515523404059. The reversal of 21515523404021 is 12040432551512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20105986960900 + 1409536443121 = 4483970^2 + 1187239^2 .

It is a cyclic number.

It is not a de Polignac number, because 21515523404021 - 2³⁰ = 21514449662197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21515823404021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10757761702010 + 10757761702011.

It is an arithmetic number, because the mean of its divisors is an integer number (10757761702011).

Almost surely, 2^{21515523404021} is an apocalyptic number.

It is an amenable number.

21515523404021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21515523404021 is an equidigital number, since it uses as much as digits as its factorization.

21515523404021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48000, while the sum is 35.

Adding to 21515523404021 its reverse (12040432551512), we get a palindrome (33555955955533).

The spelling of 21515523404021 in words is "twenty-one trillion, five hundred fifteen billion, five hundred twenty-three million, four hundred four thousand, twenty-one".