21234543457 has 2 divisors, whose sum is σ = 21234543458. Its totient is φ = 21234543456.

The previous prime is 21234543397. The next prime is 21234543487. The reversal of 21234543457 is 75434543212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11958734736 + 9275808721 = 109356^2 + 96311^2 .

It is a cyclic number.

It is not a de Polignac number, because 21234543457 - 2¹¹ = 21234541409 is a prime.

It is not a weakly prime, because it can be changed into another prime (21234543487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617271728 + 10617271729.

It is an arithmetic number, because the mean of its divisors is an integer number (10617271729).

Almost surely, 2^21234543457 is an apocalyptic number.

It is an amenable number.

21234543457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21234543457 is an equidigital number, since it uses as much as digits as its factorization.

21234543457 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 403200, while the sum is 40.

The spelling of 21234543457 in words is "twenty-one billion, two hundred thirty-four million, five hundred forty-three thousand, four hundred fifty-seven".