21705503 has 2 divisors, whose sum is σ = 21705504. Its totient is φ = 21705502.

The previous prime is 21705479. The next prime is 21705517. The reversal of 21705503 is 30550712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21705503 - 2¹⁶ = 21639967 is a prime.

It is a super-2 number, since 2×21705503² = 942257720966018, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21705553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852751 + 10852752.

It is an arithmetic number, because the mean of its divisors is an integer number (10852752).

Almost surely, 2^21705503 is an apocalyptic number.

21705503 is a deficient number, since it is larger than the sum of its proper divisors (1).

21705503 is an equidigital number, since it uses as much as digits as its factorization.

21705503 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1050, while the sum is 23.

The square root of 21705503 is about 4658.9165049397. The cubic root of 21705503 is about 278.9480211317.

The spelling of 21705503 in words is "twenty-one million, seven hundred five thousand, five hundred three".