21784491864 has 160 divisors (see below), whose sum is σ = 63488409600. Its totient is φ = 6971106240.

The previous prime is 21784491851. The next prime is 21784491983. The reversal of 21784491864 is 46819448712.

21784491864 is a `hidden beast` number, since 2 + 1 + 78 + 4 + 491 + 86 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 21784491864.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 2546907 + ... + 2555445.

It is an arithmetic number, because the mean of its divisors is an integer number (396802560).

Almost surely, 2^21784491864 is an apocalyptic number.

21784491864 is a gapful number since it is divisible by the number (24) 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 21784491864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31744204800).

21784491864 is an abundant number, since it is smaller than the sum of its proper divisors (41703917736).

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

21784491864 is a wasteful number, since it uses less digits than its factorization.

21784491864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8715 (or 8702 counting only the distinct ones).

The product of its digits is 3096576, while the sum is 54.

The spelling of 21784491864 in words is "twenty-one billion, seven hundred eighty-four million, four hundred ninety-one thousand, eight hundred sixty-four".