21143691543521 has 2 divisors, whose sum is σ = 21143691543522. Its totient is φ = 21143691543520.

The previous prime is 21143691543449. The next prime is 21143691543589. The reversal of 21143691543521 is 12534519634112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17892561601600 + 3251129941921 = 4229960^2 + 1803089^2 .

It is a cyclic number.

It is not a de Polignac number, because 21143691543521 - 2¹⁴ = 21143691527137 is a prime.

It is a super-2 number, since 2×21143691543521² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21143691543721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10571845771760 + 10571845771761.

It is an arithmetic number, because the mean of its divisors is an integer number (10571845771761).

Almost surely, 2^{21143691543521} is an apocalyptic number.

It is an amenable number.

21143691543521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21143691543521 is an equidigital number, since it uses as much as digits as its factorization.

21143691543521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 777600, while the sum is 47.

The spelling of 21143691543521 in words is "twenty-one trillion, one hundred forty-three billion, six hundred ninety-one million, five hundred forty-three thousand, five hundred twenty-one".