21644513442 has 128 divisors (see below), whose sum is σ = 52603084800. Its totient is φ = 6573571200.

The previous prime is 21644513431. The next prime is 21644513447. The reversal of 21644513442 is 24431544612.

21644513442 is a `hidden beast` number, since 2 + 1 + 644 + 5 + 1 + 3 + 4 + 4 + 2 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 21644513397 and 21644513406.

It is not an unprimeable number, because it can be changed into a prime (21644513447) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2983063 + ... + 2990309.

It is an arithmetic number, because the mean of its divisors is an integer number (410961600).

Almost surely, 2^21644513442 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21644513442, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26301542400).

21644513442 is an abundant number, since it is smaller than the sum of its proper divisors (30958571358).

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

21644513442 is a wasteful number, since it uses less digits than its factorization.

21644513442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7389 (or 7383 counting only the distinct ones).

The product of its digits is 92160, while the sum is 36.

The spelling of 21644513442 in words is "twenty-one billion, six hundred forty-four million, five hundred thirteen thousand, four hundred forty-two".