21543821148865 has 16 divisors (see below), whose sum is σ = 25950091021776. Its totient is φ = 17170079180800.

The previous prime is 21543821148803. The next prime is 21543821148869. The reversal of 21543821148865 is 56884112834512.

It can be written as a sum of positive squares in 8 ways, for example, as 2271519208336 + 19272301940529 = 1507156^2 + 4390023^2 .

It is not a de Polignac number, because 21543821148865 - 2¹⁷ = 21543821017793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21543821148869) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5009019 + ... + 8256991.

It is an arithmetic number, because the mean of its divisors is an integer number (1621880688861).

Almost surely, 2^{21543821148865} is an apocalyptic number.

It is an amenable number.

21543821148865 is a deficient number, since it is larger than the sum of its proper divisors (4406269872911).

21543821148865 is a wasteful number, since it uses less digits than its factorization.

21543821148865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3252980.

The product of its digits is 14745600, while the sum is 58.

The spelling of 21543821148865 in words is "twenty-one trillion, five hundred forty-three billion, eight hundred twenty-one million, one hundred forty-eight thousand, eight hundred sixty-five".