21366403 has 2 divisors, whose sum is σ = 21366404. Its totient is φ = 21366402.

The previous prime is 21366391. The next prime is 21366407. The reversal of 21366403 is 30466312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21366403 - 2²¹ = 19269251 is a prime.

It is not a weakly prime, because it can be changed into another prime (21366407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10683201 + 10683202.

It is an arithmetic number, because the mean of its divisors is an integer number (10683202).

Almost surely, 2^21366403 is an apocalyptic number.

21366403 is a deficient number, since it is larger than the sum of its proper divisors (1).

21366403 is an equidigital number, since it uses as much as digits as its factorization.

21366403 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 21366403 is about 4622.3806636840. The cubic root of 21366403 is about 277.4877434188.

Subtracting 21366403 from its reverse (30466312), we obtain a palindrome (9099909).

The spelling of 21366403 in words is "twenty-one million, three hundred sixty-six thousand, four hundred three".