21256620020321 has 16 divisors (see below), whose sum is σ = 24691872619008. Its totient is φ = 17921023848000.

The previous prime is 21256620020309. The next prime is 21256620020413. The reversal of 21256620020321 is 12302002665212.

It is a de Polignac number, because none of the positive numbers 2^k-21256620020321 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21256620020521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34667816 + ... + 35275638.

It is an arithmetic number, because the mean of its divisors is an integer number (1543242038688).

Almost surely, 2^{21256620020321} is an apocalyptic number.

It is an amenable number.

21256620020321 is a deficient number, since it is larger than the sum of its proper divisors (3435252598687).

21256620020321 is an equidigital number, since it uses as much as digits as its factorization.

21256620020321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 689792.

The product of its (nonzero) digits is 17280, while the sum is 32.

Adding to 21256620020321 its reverse (12302002665212), we get a palindrome (33558622685533).

The spelling of 21256620020321 in words is "twenty-one trillion, two hundred fifty-six billion, six hundred twenty million, twenty thousand, three hundred twenty-one".