21305412881 has 4 divisors (see below), whose sum is σ = 21314079600. Its totient is φ = 21296746164.

The previous prime is 21305412857. The next prime is 21305412929. The reversal of 21305412881 is 18821450312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21305412881 is a prime.

It is a super-2 number, since 2×21305412881² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21305412851) by changing a digit.

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, 4329671 + ... + 4334588.

It is an arithmetic number, because the mean of its divisors is an integer number (5328519900).

Almost surely, 2^21305412881 is an apocalyptic number.

It is an amenable number.

21305412881 is a deficient number, since it is larger than the sum of its proper divisors (8666719).

21305412881 is an equidigital number, since it uses as much as digits as its factorization.

21305412881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8666718.

The product of its (nonzero) digits is 15360, while the sum is 35.

The spelling of 21305412881 in words is "twenty-one billion, three hundred five million, four hundred twelve thousand, eight hundred eighty-one".