21641100 has 144 divisors (see below), whose sum is σ = 69995520. Its totient is φ = 5126400.

The previous prime is 21641099. The next prime is 21641107. The reversal of 21641100 is 114612.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21641100.

It is not an unprimeable number, because it can be changed into a prime (21641107) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 120811 + ... + 120989.

It is an arithmetic number, because the mean of its divisors is an integer number (486080).

Almost surely, 2^21641100 is an apocalyptic number.

21641100 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 21641100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34997760).

21641100 is an abundant number, since it is smaller than the sum of its proper divisors (48354420).

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

21641100 is a wasteful number, since it uses less digits than its factorization.

21641100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240 (or 233 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21641100 is about 4651.9995700774. Note that the first 3 decimals coincide. The cubic root of 21641100 is about 278.6718563423.

Adding to 21641100 its reverse (114612), we get a palindrome (21755712).

The spelling of 21641100 in words is "twenty-one million, six hundred forty-one thousand, one hundred".