21209603 has 2 divisors, whose sum is σ = 21209604. Its totient is φ = 21209602.

The previous prime is 21209597. The next prime is 21209609. The reversal of 21209603 is 30690212.

It is a balanced prime because it is at equal distance from previous prime (21209597) and next prime (21209609).

It is a cyclic number.

It is not a de Polignac number, because 21209603 - 2²⁰ = 20161027 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21209609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604801 + 10604802.

It is an arithmetic number, because the mean of its divisors is an integer number (10604802).

Almost surely, 2^21209603 is an apocalyptic number.

21209603 is a deficient number, since it is larger than the sum of its proper divisors (1).

21209603 is an equidigital number, since it uses as much as digits as its factorization.

21209603 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 21209603 is about 4605.3884743852. The cubic root of 21209603 is about 276.8072834004.

Adding to 21209603 its reverse (30690212), we get a palindrome (51899815).

It can be divided in two parts, 21209 and 603, that added together give a palindrome (21812).

The spelling of 21209603 in words is "twenty-one million, two hundred nine thousand, six hundred three".