21905665440 has 384 divisors, whose sum is σ = 75330984960. Its totient is φ = 5332303872.

The previous prime is 21905665433. The next prime is 21905665499. The reversal of 21905665440 is 4456650912.

It is a junction number, because it is equal to n+sod(n) for n = 21905665392 and 21905665401.

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, 32548944 + ... + 32549616.

It is an arithmetic number, because the mean of its divisors is an integer number (196174440).

Almost surely, 2^21905665440 is an apocalyptic number.

21905665440 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 21905665440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37665492480).

21905665440 is an abundant number, since it is smaller than the sum of its proper divisors (53425319520).

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

21905665440 is a wasteful number, since it uses less digits than its factorization.

21905665440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 836 (or 828 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 42.

The spelling of 21905665440 in words is "twenty-one billion, nine hundred five million, six hundred sixty-five thousand, four hundred forty".