21120829920 has 768 divisors, whose sum is σ = 83085004800. Its totient is φ = 4985487360.

The previous prime is 21120829909. The next prime is 21120829927. The reversal of 21120829920 is 2992802112.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120829927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 100098615 + ... + 100098825.

It is an arithmetic number, because the mean of its divisors is an integer number (108183600).

Almost surely, 2^21120829920 is an apocalyptic number.

21120829920 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 21120829920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41542502400).

21120829920 is an abundant number, since it is smaller than the sum of its proper divisors (61964174880).

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

21120829920 is a wasteful number, since it uses less digits than its factorization.

21120829920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328 (or 314 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The spelling of 21120829920 in words is "twenty-one billion, one hundred twenty million, eight hundred twenty-nine thousand, nine hundred twenty".