21408455520 has 384 divisors, whose sum is σ = 76488209280. Its totient is φ = 5661425664.

The previous prime is 21408455513. The next prime is 21408455531. The reversal of 21408455520 is 2555480412.

21408455520 is a `hidden beast` number, since 2 + 1 + 4 + 0 + 84 + 55 + 520 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 67534402 + ... + 67534718.

It is an arithmetic number, because the mean of its divisors is an integer number (199188045).

Almost surely, 2^21408455520 is an apocalyptic number.

21408455520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21408455520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38244104640).

21408455520 is an abundant number, since it is smaller than the sum of its proper divisors (55079753760).

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

21408455520 is an equidigital number, since it uses as much as digits as its factorization.

21408455520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546 (or 520 counting only the distinct ones).

The product of its (nonzero) digits is 64000, while the sum is 36.

The spelling of 21408455520 in words is "twenty-one billion, four hundred eight million, four hundred fifty-five thousand, five hundred twenty".