21253236553543 has 4 divisors (see below), whose sum is σ = 21253249315648. Its totient is φ = 21253223791440.

The previous prime is 21253236553501. The next prime is 21253236553597. The reversal of 21253236553543 is 34535563235212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21253236553543 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 (21253236551543) 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, 3427278 + ... + 7365643.

It is an arithmetic number, because the mean of its divisors is an integer number (5313312328912).

Almost surely, 2^{21253236553543} is an apocalyptic number.

21253236553543 is a deficient number, since it is larger than the sum of its proper divisors (12762105).

21253236553543 is a wasteful number, since it uses less digits than its factorization.

21253236553543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12762104.

The product of its digits is 9720000, while the sum is 49.

Adding to 21253236553543 its reverse (34535563235212), we get a palindrome (55788799788755).

The spelling of 21253236553543 in words is "twenty-one trillion, two hundred fifty-three billion, two hundred thirty-six million, five hundred fifty-three thousand, five hundred forty-three".