21705384924 has 72 divisors (see below), whose sum is σ = 57372456960. Its totient is φ = 6905983392.

The previous prime is 21705384913. The next prime is 21705384929. The reversal of 21705384924 is 42948350712.

21705384924 is a `hidden beast` number, since 2 + 1 + 70 + 538 + 49 + 2 + 4 = 666.

It is a super-2 number, since 2×21705384924² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21705384924.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705384929) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 369249 + ... + 423975.

It is an arithmetic number, because the mean of its divisors is an integer number (796839680).

Almost surely, 2^21705384924 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 21705384924, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28686228480).

21705384924 is an abundant number, since it is smaller than the sum of its proper divisors (35667072036).

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

21705384924 is a wasteful number, since it uses less digits than its factorization.

21705384924 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55239 (or 55234 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The spelling of 21705384924 in words is "twenty-one billion, seven hundred five million, three hundred eighty-four thousand, nine hundred twenty-four".