21404503 has 2 divisors, whose sum is σ = 21404504. Its totient is φ = 21404502.

The previous prime is 21404491. The next prime is 21404531. The reversal of 21404503 is 30540412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21404503 - 2¹⁷ = 21273431 is a prime.

It is the 4627-th Hogben number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21404543) by changing a digit.

It is a nontrivial repunit in base 4626.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702251 + 10702252.

It is an arithmetic number, because the mean of its divisors is an integer number (10702252).

Almost surely, 2^21404503 is an apocalyptic number.

21404503 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404503 is an equidigital number, since it uses as much as digits as its factorization.

21404503 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21404503 is about 4626.5000810548. The cubic root of 21404503 is about 277.6525817271.

Adding to 21404503 its reverse (30540412), we get a palindrome (51944915).

The spelling of 21404503 in words is "twenty-one million, four hundred four thousand, five hundred three".