21354661341521 has 4 divisors (see below), whose sum is σ = 21354819541044. Its totient is φ = 21354503142000.

The previous prime is 21354661341499. The next prime is 21354661341617. The reversal of 21354661341521 is 12514316645312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 691600140625 + 20663061200896 = 831625^2 + 4545664^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21354661341521 is a prime.

It is a super-2 number, since 2×21354661341521² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21354661341421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78897110 + ... + 79167311.

It is an arithmetic number, because the mean of its divisors is an integer number (5338704885261).

Almost surely, 2^{21354661341521} is an apocalyptic number.

It is an amenable number.

21354661341521 is a deficient number, since it is larger than the sum of its proper divisors (158199523).

21354661341521 is a wasteful number, since it uses less digits than its factorization.

21354661341521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158199522.

The product of its digits is 518400, while the sum is 44.

Adding to 21354661341521 its reverse (12514316645312), we get a palindrome (33868977986833).

The spelling of 21354661341521 in words is "twenty-one trillion, three hundred fifty-four billion, six hundred sixty-one million, three hundred forty-one thousand, five hundred twenty-one".