21720043800 has 864 divisors, whose sum is σ = 96285243600. Its totient is φ = 4337141760.

The previous prime is 21720043753. The next prime is 21720043823. The reversal of 21720043800 is 834002712.

21720043800 is a `hidden beast` number, since 21 + 7 + 200 + 438 + 0 + 0 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 21784902 + ... + 21785898.

Almost surely, 2^21720043800 is an apocalyptic number.

21720043800 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 21720043800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (48142621800).

21720043800 is an abundant number, since it is smaller than the sum of its proper divisors (74565199800).

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

21720043800 is a wasteful number, since it uses less digits than its factorization.

21720043800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1065 (or 1046 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The spelling of 21720043800 in words is "twenty-one billion, seven hundred twenty million, forty-three thousand, eight hundred".