21015521453 has 2 divisors, whose sum is σ = 21015521454. Its totient is φ = 21015521452.

The previous prime is 21015521447. The next prime is 21015521503. The reversal of 21015521453 is 35412551012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17890935049 + 3124586404 = 133757^2 + 55898^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015521453 - 2¹⁶ = 21015455917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21015521353) 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, 10507760726 + 10507760727.

It is an arithmetic number, because the mean of its divisors is an integer number (10507760727).

Almost surely, 2^21015521453 is an apocalyptic number.

It is an amenable number.

21015521453 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015521453 is an equidigital number, since it uses as much as digits as its factorization.

21015521453 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6000, while the sum is 29.

The spelling of 21015521453 in words is "twenty-one billion, fifteen million, five hundred twenty-one thousand, four hundred fifty-three".