21456403 has 2 divisors, whose sum is σ = 21456404. Its totient is φ = 21456402.

The previous prime is 21456373. The next prime is 21456419. The reversal of 21456403 is 30465412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21456403 - 2⁹ = 21455891 is a prime.

It is not a weakly prime, because it can be changed into another prime (21456103) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728201 + 10728202.

It is an arithmetic number, because the mean of its divisors is an integer number (10728202).

Almost surely, 2^21456403 is an apocalyptic number.

21456403 is a deficient number, since it is larger than the sum of its proper divisors (1).

21456403 is an equidigital number, since it uses as much as digits as its factorization.

21456403 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21456403 is about 4632.1056766874. The cubic root of 21456403 is about 277.8768108338.

Subtracting 21456403 from its reverse (30465412), we obtain a palindrome (9009009).

The spelling of 21456403 in words is "twenty-one million, four hundred fifty-six thousand, four hundred three".