21543720105 has 16 divisors (see below), whose sum is σ = 35120329920. Its totient is φ = 11273191488.

The previous prime is 21543720091. The next prime is 21543720127. The reversal of 21543720105 is 50102734512.

It is not a de Polignac number, because 21543720105 - 2⁴ = 21543720089 is a prime.

It is a super-2 number, since 2×21543720105² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13548715 + ... + 13550304.

It is an arithmetic number, because the mean of its divisors is an integer number (2195020620).

Almost surely, 2^21543720105 is an apocalyptic number.

It is an amenable number.

21543720105 is a deficient number, since it is larger than the sum of its proper divisors (13576609815).

21543720105 is a wasteful number, since it uses less digits than its factorization.

21543720105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27099080.

The product of its (nonzero) digits is 8400, while the sum is 30.

The spelling of 21543720105 in words is "twenty-one billion, five hundred forty-three million, seven hundred twenty thousand, one hundred five".