21544100165 has 16 divisors (see below), whose sum is σ = 29558971008. Its totient is φ = 14766709056.

The previous prime is 21544100159. The next prime is 21544100167. The reversal of 21544100165 is 56100144512.

It is a cyclic number.

It is not a de Polignac number, because 21544100165 - 2²⁰ = 21543051589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21544100167) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50267 + ... + 213576.

It is an arithmetic number, because the mean of its divisors is an integer number (1847435688).

Almost surely, 2^21544100165 is an apocalyptic number.

It is an amenable number.

21544100165 is a deficient number, since it is larger than the sum of its proper divisors (8014870843).

21544100165 is a wasteful number, since it uses less digits than its factorization.

21544100165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266188.

The product of its (nonzero) digits is 4800, while the sum is 29.

Adding to 21544100165 its reverse (56100144512), we get a palindrome (77644244677).

The spelling of 21544100165 in words is "twenty-one billion, five hundred forty-four million, one hundred thousand, one hundred sixty-five".