21015521503 has 2 divisors, whose sum is σ = 21015521504. Its totient is φ = 21015521502.

The previous prime is 21015521453. The next prime is 21015521507. The reversal of 21015521503 is 30512551012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21015521503 - 2²¹ = 21013424351 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21015521507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507760751 + 10507760752.

It is an arithmetic number, because the mean of its divisors is an integer number (10507760752).

Almost surely, 2^21015521503 is an apocalyptic number.

21015521503 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015521503 is an equidigital number, since it uses as much as digits as its factorization.

21015521503 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1500, while the sum is 25.

The spelling of 21015521503 in words is "twenty-one billion, fifteen million, five hundred twenty-one thousand, five hundred three".