21408080 has 20 divisors (see below), whose sum is σ = 49773972. Its totient is φ = 8563200.

The previous prime is 21408071. The next prime is 21408097. The reversal of 21408080 is 8080412.

It can be written as a sum of positive squares in 2 ways, for example, as 2676496 + 18731584 = 1636^2 + 4328^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133721 + ... + 133880.

Almost surely, 2^21408080 is an apocalyptic number.

21408080 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21408080 is an abundant number, since it is smaller than the sum of its proper divisors (28365892).

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

21408080 is a wasteful number, since it uses less digits than its factorization.

21408080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 267614 (or 267608 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 23.

The square root of 21408080 is about 4626.8866422250. The cubic root of 21408080 is about 277.6680474442.

Adding to 21408080 its reverse (8080412), we get a palindrome (29488492).

The spelling of 21408080 in words is "twenty-one million, four hundred eight thousand, eighty".