21555013312 has 112 divisors (see below), whose sum is σ = 50383001088. Its totient is φ = 8957306880.

The previous prime is 21555013301. The next prime is 21555013321. The reversal of 21555013312 is 21331055512.

It is a tau number, because it is divible by the number of its divisors (112).

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3063943 + ... + 3070969.

It is an arithmetic number, because the mean of its divisors is an integer number (449848224).

Almost surely, 2^21555013312 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21555013312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25191500544).

21555013312 is an abundant number, since it is smaller than the sum of its proper divisors (28827987776).

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

21555013312 is a wasteful number, since it uses less digits than its factorization.

21555013312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7254 (or 7244 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 28.

Adding to 21555013312 its reverse (21331055512), we get a palindrome (42886068824).

The spelling of 21555013312 in words is "twenty-one billion, five hundred fifty-five million, thirteen thousand, three hundred twelve".