21211202521 has 2 divisors, whose sum is σ = 21211202522. Its totient is φ = 21211202520.

The previous prime is 21211202503. The next prime is 21211202543. The reversal of 21211202521 is 12520211212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20523714121 + 687488400 = 143261^2 + 26220^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211202521 - 2⁵ = 21211202489 is a prime.

It is a super-2 number, since 2×21211202521² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21211202921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605601260 + 10605601261.

It is an arithmetic number, because the mean of its divisors is an integer number (10605601261).

Almost surely, 2^21211202521 is an apocalyptic number.

It is an amenable number.

21211202521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211202521 is an equidigital number, since it uses as much as digits as its factorization.

21211202521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 160, while the sum is 19.

Adding to 21211202521 its reverse (12520211212), we get a palindrome (33731413733).

The spelling of 21211202521 in words is "twenty-one billion, two hundred eleven million, two hundred two thousand, five hundred twenty-one".