21530711723281 has 2 divisors, whose sum is σ = 21530711723282. Its totient is φ = 21530711723280.

The previous prime is 21530711723251. The next prime is 21530711723333. The reversal of 21530711723281 is 18232711703512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16792292665600 + 4738419057681 = 4097840^2 + 2176791^2 .

It is a cyclic number.

It is not a de Polignac number, because 21530711723281 - 2⁵ = 21530711723249 is a prime.

It is a super-2 number, since 2×21530711723281² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21530711723251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765355861640 + 10765355861641.

It is an arithmetic number, because the mean of its divisors is an integer number (10765355861641).

Almost surely, 2^{21530711723281} is an apocalyptic number.

It is an amenable number.

21530711723281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21530711723281 is an equidigital number, since it uses as much as digits as its factorization.

21530711723281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 141120, while the sum is 43.

The spelling of 21530711723281 in words is "twenty-one trillion, five hundred thirty billion, seven hundred eleven million, seven hundred twenty-three thousand, two hundred eighty-one".