21243305453 has 4 divisors (see below), whose sum is σ = 21462308700. Its totient is φ = 21024302208.

The previous prime is 21243305411. The next prime is 21243305459. The reversal of 21243305453 is 35450334212.

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 15246816484 + 5996488969 = 123478^2 + 77437^2 .

It is a cyclic number.

It is not a de Polignac number, because 21243305453 - 2¹⁴ = 21243289069 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243305459) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109501478 + ... + 109501671.

It is an arithmetic number, because the mean of its divisors is an integer number (5365577175).

Almost surely, 2^21243305453 is an apocalyptic number.

It is an amenable number.

21243305453 is a deficient number, since it is larger than the sum of its proper divisors (219003247).

21243305453 is an equidigital number, since it uses as much as digits as its factorization.

21243305453 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219003246.

The product of its (nonzero) digits is 43200, while the sum is 32.

Adding to 21243305453 its reverse (35450334212), we get a palindrome (56693639665).

The spelling of 21243305453 in words is "twenty-one billion, two hundred forty-three million, three hundred five thousand, four hundred fifty-three".