21211081447 has 4 divisors (see below), whose sum is σ = 21246026176. Its totient is φ = 21176136720.

The previous prime is 21211081417. The next prime is 21211081457. The reversal of 21211081447 is 74418011212.

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-21211081447 is a prime.

It is a super-2 number, since 2×21211081447² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211081417) 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, 17471454 + ... + 17472667.

It is an arithmetic number, because the mean of its divisors is an integer number (5311506544).

Almost surely, 2^21211081447 is an apocalyptic number.

21211081447 is a deficient number, since it is larger than the sum of its proper divisors (34944729).

21211081447 is an equidigital number, since it uses as much as digits as its factorization.

21211081447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34944728.

The product of its (nonzero) digits is 3584, while the sum is 31.

Adding to 21211081447 its reverse (74418011212), we get a palindrome (95629092659).

The spelling of 21211081447 in words is "twenty-one billion, two hundred eleven million, eighty-one thousand, four hundred forty-seven".