21408199 has 4 divisors (see below), whose sum is σ = 21701536. Its totient is φ = 21114864.

The previous prime is 21408181. The next prime is 21408227. The reversal of 21408199 is 99180412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21408199 - 2⁷ = 21408071 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21408169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 146559 + ... + 146704.

It is an arithmetic number, because the mean of its divisors is an integer number (5425384).

Almost surely, 2^21408199 is an apocalyptic number.

21408199 is a deficient number, since it is larger than the sum of its proper divisors (293337).

21408199 is an equidigital number, since it uses as much as digits as its factorization.

21408199 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 293336.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 21408199 is about 4626.8995018262. The cubic root of 21408199 is about 277.6685619296.

The spelling of 21408199 in words is "twenty-one million, four hundred eight thousand, one hundred ninety-nine".