21555325440 has 480 divisors, whose sum is σ = 86246462016. Its totient is φ = 4917166080.

The previous prime is 21555325433. The next prime is 21555325453. The reversal of 21555325440 is 4452355512.

21555325440 is a `hidden beast` number, since 2 + 15 + 553 + 2 + 54 + 40 = 666.

It is a tau number, because it is divible by the number of its divisors (480).

It is a super-2 number, since 2×21555325440² (a number of 21 digits) contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 21555325395 and 21555325404.

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, 4305979 + ... + 4310981.

Almost surely, 2^21555325440 is an apocalyptic number.

21555325440 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 21555325440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43123231008).

21555325440 is an abundant number, since it is smaller than the sum of its proper divisors (64691136576).

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

21555325440 is a wasteful number, since it uses less digits than its factorization.

21555325440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5060 (or 5041 counting only the distinct ones).

The product of its (nonzero) digits is 120000, while the sum is 36.

The spelling of 21555325440 in words is "twenty-one billion, five hundred fifty-five million, three hundred twenty-five thousand, four hundred forty".