21521665943 has 2 divisors, whose sum is σ = 21521665944. Its totient is φ = 21521665942.

The previous prime is 21521665903. The next prime is 21521666011. The reversal of 21521665943 is 34956612512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21521665943 - 2¹⁴ = 21521649559 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21521665894 and 21521665903.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21521665903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760832971 + 10760832972.

It is an arithmetic number, because the mean of its divisors is an integer number (10760832972).

Almost surely, 2^21521665943 is an apocalyptic number.

21521665943 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521665943 is an equidigital number, since it uses as much as digits as its factorization.

21521665943 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 388800, while the sum is 44.

The spelling of 21521665943 in words is "twenty-one billion, five hundred twenty-one million, six hundred sixty-five thousand, nine hundred forty-three".