21408084 has 24 divisors (see below), whose sum is σ = 55502720. Its totient is φ = 7135992.

The previous prime is 21408071. The next prime is 21408097. The reversal of 21408084 is 48080412.

It is an interprime number because it is at equal distance from previous prime (21408071) and next prime (21408097).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 99004 + ... + 99219.

Almost surely, 2^21408084 is an apocalyptic number.

It is an amenable number.

21408084 is an abundant number, since it is smaller than the sum of its proper divisors (34094636).

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

21408084 is a wasteful number, since it uses less digits than its factorization.

21408084 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198236 (or 198228 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 21408084 is about 4626.8870744811. The cubic root of 21408084 is about 277.6680647379.

Adding to 21408084 its reverse (48080412), we get a palindrome (69488496).

The spelling of 21408084 in words is "twenty-one million, four hundred eight thousand, eighty-four".