21065634481 has 4 divisors (see below), whose sum is σ = 21792035700. Its totient is φ = 20339233264.

The previous prime is 21065634451. The next prime is 21065634497. The reversal of 21065634481 is 18443656012.

It is a happy number.

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 10521630625 + 10544003856 = 102575^2 + 102684^2 .

It is a cyclic number.

It is not a de Polignac number, because 21065634481 - 2¹⁷ = 21065503409 is a prime.

It is a super-2 number, since 2×21065634481² (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 (21065634451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 363200566 + ... + 363200623.

It is an arithmetic number, because the mean of its divisors is an integer number (5448008925).

Almost surely, 2^21065634481 is an apocalyptic number.

It is an amenable number.

21065634481 is a deficient number, since it is larger than the sum of its proper divisors (726401219).

21065634481 is an equidigital number, since it uses as much as digits as its factorization.

21065634481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 726401218.

The product of its (nonzero) digits is 138240, while the sum is 40.

The spelling of 21065634481 in words is "twenty-one billion, sixty-five million, six hundred thirty-four thousand, four hundred eighty-one".