21408306 has 8 divisors (see below), whose sum is σ = 42816624. Its totient is φ = 7136100.

The previous prime is 21408301. The next prime is 21408319. The reversal of 21408306 is 60380412.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

21408306 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21408301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1784020 + ... + 1784031.

It is an arithmetic number, because the mean of its divisors is an integer number (5352078).

Almost surely, 2^21408306 is an apocalyptic number.

21408306 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21408306 is a wasteful number, since it uses less digits than its factorization.

21408306 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3568056.

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21408306 is about 4626.9110646305. The cubic root of 21408306 is about 277.6690245326.

Adding to 21408306 its reverse (60380412), we get a palindrome (81788718).

The spelling of 21408306 in words is "twenty-one million, four hundred eight thousand, three hundred six".