21019903 has 2 divisors, whose sum is σ = 21019904. Its totient is φ = 21019902.

The previous prime is 21019879. The next prime is 21019919. The reversal of 21019903 is 30991012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21019903 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21019963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10509951 + 10509952.

It is an arithmetic number, because the mean of its divisors is an integer number (10509952).

Almost surely, 2^21019903 is an apocalyptic number.

21019903 is a deficient number, since it is larger than the sum of its proper divisors (1).

21019903 is an equidigital number, since it uses as much as digits as its factorization.

21019903 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 21019903 is about 4584.7467759954. The cubic root of 21019903 is about 275.9795502247.

The spelling of 21019903 in words is "twenty-one million, nineteen thousand, nine hundred three".