21289100 has 72 divisors (see below), whose sum is σ = 55933920. Its totient is φ = 6865920.

The previous prime is 21289091. The next prime is 21289123. The reversal of 21289100 is 198212.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11006 + ... + 12794.

It is an arithmetic number, because the mean of its divisors is an integer number (776860).

Almost surely, 2^21289100 is an apocalyptic number.

21289100 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 21289100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27966960).

21289100 is an abundant number, since it is smaller than the sum of its proper divisors (34644820).

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

21289100 is a wasteful number, since it uses less digits than its factorization.

21289100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1827 (or 1820 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 21289100 is about 4614.0112700339. The cubic root of 21289100 is about 277.1526916025.

The spelling of 21289100 in words is "twenty-one million, two hundred eighty-nine thousand, one hundred".