21408833 has 2 divisors, whose sum is σ = 21408834. Its totient is φ = 21408832.

The previous prime is 21408823. The next prime is 21408841. The reversal of 21408833 is 33880412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20584369 + 824464 = 4537^2 + 908^2 .

It is a cyclic number.

It is not a de Polignac number, because 21408833 - 2¹⁰ = 21407809 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21408796 and 21408805.

It is not a weakly prime, because it can be changed into another prime (21408823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704416 + 10704417.

It is an arithmetic number, because the mean of its divisors is an integer number (10704417).

Almost surely, 2^21408833 is an apocalyptic number.

It is an amenable number.

21408833 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408833 is an equidigital number, since it uses as much as digits as its factorization.

21408833 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 21408833 is about 4626.9680137213. The cubic root of 21408833 is about 277.6713029376.

The spelling of 21408833 in words is "twenty-one million, four hundred eight thousand, eight hundred thirty-three".