21768531840 has 512 divisors, whose sum is σ = 85343155200. Its totient is φ = 5199667200.

The previous prime is 21768531817. The next prime is 21768531847. The reversal of 21768531840 is 4813586712.

21768531840 is a `hidden beast` number, since 2 + 1 + 76 + 8 + 531 + 8 + 40 = 666.

It is a super-3 number, since 3×21768531840³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21768531847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 13494874 + ... + 13496486.

It is an arithmetic number, because the mean of its divisors is an integer number (166685850).

Almost surely, 2^21768531840 is an apocalyptic number.

21768531840 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 21768531840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42671577600).

21768531840 is an abundant number, since it is smaller than the sum of its proper divisors (63574623360).

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

21768531840 is a wasteful number, since it uses less digits than its factorization.

21768531840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1723 (or 1705 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 21768531840 in words is "twenty-one billion, seven hundred sixty-eight million, five hundred thirty-one thousand, eight hundred forty".