21531501542543 has 2 divisors, whose sum is σ = 21531501542544. Its totient is φ = 21531501542542.

The previous prime is 21531501542501. The next prime is 21531501542561. The reversal of 21531501542543 is 34524510513512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21531501542543 - 2¹² = 21531501538447 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21531501542543.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21531501542143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765750771271 + 10765750771272.

It is an arithmetic number, because the mean of its divisors is an integer number (10765750771272).

Almost surely, 2^{21531501542543} is an apocalyptic number.

21531501542543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531501542543 is an equidigital number, since it uses as much as digits as its factorization.

21531501542543 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360000, while the sum is 41.

The spelling of 21531501542543 in words is "twenty-one trillion, five hundred thirty-one billion, five hundred one million, five hundred forty-two thousand, five hundred forty-three".