21100240 has 80 divisors (see below), whose sum is σ = 57496320. Its totient is φ = 7050240.

The previous prime is 21100231. The next prime is 21100253. The reversal of 21100240 is 4200112.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22501 + ... + 23419.

It is an arithmetic number, because the mean of its divisors is an integer number (718704).

Almost surely, 2^21100240 is an apocalyptic number.

21100240 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 21100240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28748160).

21100240 is an abundant number, since it is smaller than the sum of its proper divisors (36396080).

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

21100240 is a wasteful number, since it uses less digits than its factorization.

21100240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 980 (or 974 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21100240 is about 4593.4997550887. The cubic root of 21100240 is about 276.3306965168.

Adding to 21100240 its reverse (4200112), we get a palindrome (25300352).

The spelling of 21100240 in words is "twenty-one million, one hundred thousand, two hundred forty".