21256215004121 has 2 divisors, whose sum is σ = 21256215004122. Its totient is φ = 21256215004120.

The previous prime is 21256215004067. The next prime is 21256215004159. The reversal of 21256215004121 is 12140051265212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19538070795721 + 1718144208400 = 4420189^2 + 1310780^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256215004121 - 2³⁰ = 21255141262297 is a prime.

It is not a weakly prime, because it can be changed into another prime (21256215004421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10628107502060 + 10628107502061.

It is an arithmetic number, because the mean of its divisors is an integer number (10628107502061).

Almost surely, 2^{21256215004121} is an apocalyptic number.

It is an amenable number.

21256215004121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256215004121 is an equidigital number, since it uses as much as digits as its factorization.

21256215004121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9600, while the sum is 32.

Adding to 21256215004121 its reverse (12140051265212), we get a palindrome (33396266269333).

The spelling of 21256215004121 in words is "twenty-one trillion, two hundred fifty-six billion, two hundred fifteen million, four thousand, one hundred twenty-one".