21261232153445 has 4 divisors (see below), whose sum is σ = 25513478584140. Its totient is φ = 17008985722752.

The previous prime is 21261232153387. The next prime is 21261232153507. The reversal of 21261232153445 is 54435123216212.

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 9950346609889 + 11310885543556 = 3154417^2 + 3363166^2 .

It is a cyclic number.

It is not a de Polignac number, because 21261232153445 - 2¹⁸ = 21261231891301 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2126123215340 + ... + 2126123215349.

It is an arithmetic number, because the mean of its divisors is an integer number (6378369646035).

Almost surely, 2^{21261232153445} is an apocalyptic number.

It is an amenable number.

21261232153445 is a deficient number, since it is larger than the sum of its proper divisors (4252246430695).

21261232153445 is an equidigital number, since it uses as much as digits as its factorization.

21261232153445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4252246430694.

The product of its digits is 345600, while the sum is 41.

Adding to 21261232153445 its reverse (54435123216212), we get a palindrome (75696355369657).

The spelling of 21261232153445 in words is "twenty-one trillion, two hundred sixty-one billion, two hundred thirty-two million, one hundred fifty-three thousand, four hundred forty-five".