21009859678081 has 4 divisors (see below), whose sum is σ = 21456877969152. Its totient is φ = 20562841387012.

The previous prime is 21009859678051. The next prime is 21009859678111. The reversal of 21009859678081 is 18087695890012.

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 an interprime number because it is at equal distance from previous prime (21009859678051) and next prime (21009859678111).

It is a cyclic number.

It is not a de Polignac number, because 21009859678081 - 2¹¹ = 21009859676033 is a prime.

It is a super-2 number, since 2×21009859678081² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21009859678001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 223509145465 + ... + 223509145558.

It is an arithmetic number, because the mean of its divisors is an integer number (5364219492288).

Almost surely, 2^{21009859678081} is an apocalyptic number.

It is an amenable number.

21009859678081 is a deficient number, since it is larger than the sum of its proper divisors (447018291071).

21009859678081 is an equidigital number, since it uses as much as digits as its factorization.

21009859678081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 447018291070.

The product of its (nonzero) digits is 17418240, while the sum is 64.

The spelling of 21009859678081 in words is "twenty-one trillion, nine billion, eight hundred fifty-nine million, six hundred seventy-eight thousand, eighty-one".