21855628081 has 4 divisors (see below), whose sum is σ = 24977860672. Its totient is φ = 18733395492.

The previous prime is 21855628079. The next prime is 21855628127. The reversal of 21855628081 is 18082655812.

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 not a de Polignac number, because 21855628081 - 2¹ = 21855628079 is a prime.

It is a super-2 number, since 2×21855628081² (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 (21855628381) 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, 1561116285 + ... + 1561116298.

It is an arithmetic number, because the mean of its divisors is an integer number (6244465168).

Almost surely, 2^21855628081 is an apocalyptic number.

It is an amenable number.

21855628081 is a deficient number, since it is larger than the sum of its proper divisors (3122232591).

21855628081 is an equidigital number, since it uses as much as digits as its factorization.

21855628081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3122232590.

The product of its (nonzero) digits is 307200, while the sum is 46.

The spelling of 21855628081 in words is "twenty-one billion, eight hundred fifty-five million, six hundred twenty-eight thousand, eighty-one".