21121335215521 has 2 divisors, whose sum is σ = 21121335215522. Its totient is φ = 21121335215520.

The previous prime is 21121335215501. The next prime is 21121335215527. The reversal of 21121335215521 is 12551253312112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13438676174400 + 7682659041121 = 3665880^2 + 2771761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121335215521 - 2²³ = 21121326826913 is a prime.

It is a super-2 number, since 2×21121335215521² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21121335215527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560667607760 + 10560667607761.

It is an arithmetic number, because the mean of its divisors is an integer number (10560667607761).

Almost surely, 2^{21121335215521} is an apocalyptic number.

It is an amenable number.

21121335215521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121335215521 is an equidigital number, since it uses as much as digits as its factorization.

21121335215521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18000, while the sum is 34.

Adding to 21121335215521 its reverse (12551253312112), we get a palindrome (33672588527633).

The spelling of 21121335215521 in words is "twenty-one trillion, one hundred twenty-one billion, three hundred thirty-five million, two hundred fifteen thousand, five hundred twenty-one".