21126528221 has 2 divisors, whose sum is σ = 21126528222. Its totient is φ = 21126528220.

The previous prime is 21126528197. The next prime is 21126528229. The reversal of 21126528221 is 12282562112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17341202596 + 3785325625 = 131686^2 + 61525^2 .

It is a cyclic number.

It is not a de Polignac number, because 21126528221 - 2¹⁴ = 21126511837 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21126528229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10563264110 + 10563264111.

It is an arithmetic number, because the mean of its divisors is an integer number (10563264111).

Almost surely, 2^21126528221 is an apocalyptic number.

It is an amenable number.

21126528221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21126528221 is an equidigital number, since it uses as much as digits as its factorization.

21126528221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7680, while the sum is 32.

The spelling of 21126528221 in words is "twenty-one billion, one hundred twenty-six million, five hundred twenty-eight thousand, two hundred twenty-one".