21008880 has 60 divisors (see below), whose sum is σ = 70557240. Its totient is φ = 5602176.

The previous prime is 21008879. The next prime is 21008887. The reversal of 21008880 is 8880012.

It is a tau number, because it is divible by the number of its divisors (60).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21008887) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13870 + ... + 15309.

It is an arithmetic number, because the mean of its divisors is an integer number (1175954).

Almost surely, 2^21008880 is an apocalyptic number.

21008880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21008880 is an abundant number, since it is smaller than the sum of its proper divisors (49548360).

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

21008880 is a wasteful number, since it uses less digits than its factorization.

21008880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29198 (or 29189 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 27.

The square root of 21008880 is about 4583.5444799849. The cubic root of 21008880 is about 275.9312998512.

Adding to 21008880 its reverse (8880012), we get a palindrome (29888892).

The spelling of 21008880 in words is "twenty-one million, eight thousand, eight hundred eighty".