21408357697920 has 384 divisors, whose sum is σ = 76796913342240. Its totient is φ = 5698977398784.

The previous prime is 21408357697897. The next prime is 21408357697949. The reversal of 21408357697920 is 2979675380412.

21408357697920 is a `hidden beast` number, since 2 + 1 + 408 + 3 + 57 + 6 + 97 + 92 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 89615754 + ... + 89854326.

It is a 2-persistent number, because it is pandigital, and so is 2⋅21408357697920 = 42816715395840, but 3⋅21408357697920 = 64225073093760 is not.

Almost surely, 2^{21408357697920} is an apocalyptic number.

21408357697920 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 21408357697920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38398456671120).

21408357697920 is an abundant number, since it is smaller than the sum of its proper divisors (55388555644320).

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

21408357697920 is an equidigital number, since it uses as much as digits as its factorization.

21408357697920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 239184 (or 239160 counting only the distinct ones).

The product of its (nonzero) digits is 45722880, while the sum is 63.

The spelling of 21408357697920 in words is "twenty-one trillion, four hundred eight billion, three hundred fifty-seven million, six hundred ninety-seven thousand, nine hundred twenty".