21253043500565 has 32 divisors (see below), whose sum is σ = 27937991854080. Its totient is φ = 15448852952064.

The previous prime is 21253043500553. The next prime is 21253043500621. The reversal of 21253043500565 is 56500534035212.

It is a cyclic number.

It is not a de Polignac number, because 21253043500565 - 2¹⁸ = 21253043238421 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 23081804 + ... + 23984906.

It is an arithmetic number, because the mean of its divisors is an integer number (873062245440).

Almost surely, 2^{21253043500565} is an apocalyptic number.

It is an amenable number.

21253043500565 is a deficient number, since it is larger than the sum of its proper divisors (6684948353515).

21253043500565 is a wasteful number, since it uses less digits than its factorization.

21253043500565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 912701.

The product of its (nonzero) digits is 540000, while the sum is 41.

Adding to 21253043500565 its reverse (56500534035212), we get a palindrome (77753577535777).

The spelling of 21253043500565 in words is "twenty-one trillion, two hundred fifty-three billion, forty-three million, five hundred thousand, five hundred sixty-five".