21688903 has 2 divisors, whose sum is σ = 21688904. Its totient is φ = 21688902.

The previous prime is 21688883. The next prime is 21688921. The reversal of 21688903 is 30988612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21688903 - 2⁹ = 21688391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21688963) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10844451 + 10844452.

It is an arithmetic number, because the mean of its divisors is an integer number (10844452).

Almost surely, 2^21688903 is an apocalyptic number.

21688903 is a deficient number, since it is larger than the sum of its proper divisors (1).

21688903 is an equidigital number, since it uses as much as digits as its factorization.

21688903 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21688903 is about 4657.1346340856. The cubic root of 21688903 is about 278.8768914262.

The spelling of 21688903 in words is "twenty-one million, six hundred eighty-eight thousand, nine hundred three".