21243403 has 2 divisors, whose sum is σ = 21243404. Its totient is φ = 21243402.

The previous prime is 21243361. The next prime is 21243437. The reversal of 21243403 is 30434212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21243403 is a prime.

It is not a weakly prime, because it can be changed into another prime (21243473) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621701 + 10621702.

It is an arithmetic number, because the mean of its divisors is an integer number (10621702).

Almost surely, 2^21243403 is an apocalyptic number.

21243403 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243403 is an equidigital number, since it uses as much as digits as its factorization.

21243403 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 21243403 is about 4609.0566279880. The cubic root of 21243403 is about 276.9542470276.

Adding to 21243403 its reverse (30434212), we get a palindrome (51677615).

The spelling of 21243403 in words is "twenty-one million, two hundred forty-three thousand, four hundred three".