21688747440 has 160 divisors (see below), whose sum is σ = 69042456000. Its totient is φ = 5628887040.

The previous prime is 21688747429. The next prime is 21688747459. The reversal of 21688747440 is 4474788612.

It is a Cunningham number, because it is equal to 147271²-1.

It is a super-2 number, since 2×21688747440² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4415706 + ... + 4420614.

It is an arithmetic number, because the mean of its divisors is an integer number (431515350).

Almost surely, 2^21688747440 is an apocalyptic number.

21688747440 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 21688747440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34521228000).

21688747440 is an abundant number, since it is smaller than the sum of its proper divisors (47353708560).

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

21688747440 is a wasteful number, since it uses less digits than its factorization.

21688747440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5415 (or 5409 counting only the distinct ones).

The product of its (nonzero) digits is 2408448, while the sum is 51.

The spelling of 21688747440 in words is "twenty-one billion, six hundred eighty-eight million, seven hundred forty-seven thousand, four hundred forty".