21544125905 has 4 divisors (see below), whose sum is σ = 25852951092. Its totient is φ = 17235300720.

The previous prime is 21544125881. The next prime is 21544125917. The reversal of 21544125905 is 50952144512.

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 3050573824 + 18493552081 = 55232^2 + 135991^2 .

It is not a de Polignac number, because 21544125905 - 2²⁰ = 21543077329 is a prime.

It is a super-2 number, since 2×21544125905² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2154412586 + ... + 2154412595.

It is an arithmetic number, because the mean of its divisors is an integer number (6463237773).

Almost surely, 2^21544125905 is an apocalyptic number.

It is an amenable number.

21544125905 is a deficient number, since it is larger than the sum of its proper divisors (4308825187).

21544125905 is an equidigital number, since it uses as much as digits as its factorization.

21544125905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4308825186.

The product of its (nonzero) digits is 72000, while the sum is 38.

The spelling of 21544125905 in words is "twenty-one billion, five hundred forty-four million, one hundred twenty-five thousand, nine hundred five".