21531204523417 has 2 divisors, whose sum is σ = 21531204523418. Its totient is φ = 21531204523416.

The previous prime is 21531204523267. The next prime is 21531204523441. The reversal of 21531204523417 is 71432540213512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11158399095561 + 10372805427856 = 3340419^2 + 3220684^2 .

It is a cyclic number.

It is not a de Polignac number, because 21531204523417 - 2³⁵ = 21496844785049 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21531204523417.

It is not a weakly prime, because it can be changed into another prime (21531204523457) 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, 10765602261708 + 10765602261709.

It is an arithmetic number, because the mean of its divisors is an integer number (10765602261709).

Almost surely, 2^{21531204523417} is an apocalyptic number.

It is an amenable number.

21531204523417 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531204523417 is an equidigital number, since it uses as much as digits as its factorization.

21531204523417 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 201600, while the sum is 40.

Adding to 21531204523417 its reverse (71432540213512), we get a palindrome (92963744736929).

The spelling of 21531204523417 in words is "twenty-one trillion, five hundred thirty-one billion, two hundred four million, five hundred twenty-three thousand, four hundred seventeen".