21655444608 has 384 divisors, whose sum is σ = 74850048000. Its totient is φ = 6104097792.

The previous prime is 21655444567. The next prime is 21655444621. The reversal of 21655444608 is 80644455612.

It is a happy number.

21655444608 is a `hidden beast` number, since 2 + 1 + 65 + 544 + 46 + 0 + 8 = 666.

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

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

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, 17199883 + ... + 17201141.

It is an arithmetic number, because the mean of its divisors is an integer number (194922000).

Almost surely, 2^21655444608 is an apocalyptic number.

21655444608 is a gapful number since it is divisible by the number (28) 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 21655444608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37425024000).

21655444608 is an abundant number, since it is smaller than the sum of its proper divisors (53194603392).

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

21655444608 is an equidigital number, since it uses as much as digits as its factorization.

21655444608 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1374 (or 1350 counting only the distinct ones).

The product of its (nonzero) digits is 921600, while the sum is 45.

It can be divided in two parts, 216554 and 44608, that added together give a palindrome (261162).

The spelling of 21655444608 in words is "twenty-one billion, six hundred fifty-five million, four hundred forty-four thousand, six hundred eight".