21008903 has 2 divisors, whose sum is σ = 21008904. Its totient is φ = 21008902.

The previous prime is 21008893. The next prime is 21008941. The reversal of 21008903 is 30980012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21008903 - 2⁴ = 21008887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21008203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504451 + 10504452.

It is an arithmetic number, because the mean of its divisors is an integer number (10504452).

Almost surely, 2^21008903 is an apocalyptic number.

21008903 is a deficient number, since it is larger than the sum of its proper divisors (1).

21008903 is an equidigital number, since it uses as much as digits as its factorization.

21008903 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21008903 is about 4583.5469889595. The cubic root of 21008903 is about 275.9314005454.

Adding to 21008903 its reverse (30980012), we get a palindrome (51988915).

The spelling of 21008903 in words is "twenty-one million, eight thousand, nine hundred three".