21531543525505 has 16 divisors (see below), whose sum is σ = 27861943619664. Its totient is φ = 15879322874880.

The previous prime is 21531543525413. The next prime is 21531543525529. The reversal of 21531543525505 is 50552534513512.

It can be written as a sum of positive squares in 8 ways, for example, as 5414072697856 + 16117470827649 = 2326816^2 + 4014657^2 .

It is not a de Polignac number, because 21531543525505 - 2²⁵ = 21531509971073 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 217594764 + ... + 217693693.

It is an arithmetic number, because the mean of its divisors is an integer number (1741371476229).

Almost surely, 2^{21531543525505} is an apocalyptic number.

It is an amenable number.

21531543525505 is a deficient number, since it is larger than the sum of its proper divisors (6330400094159).

21531543525505 is a wasteful number, since it uses less digits than its factorization.

21531543525505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 435289236.

The product of its (nonzero) digits is 2250000, while the sum is 46.

The spelling of 21531543525505 in words is "twenty-one trillion, five hundred thirty-one billion, five hundred forty-three million, five hundred twenty-five thousand, five hundred five".