21103440 has 40 divisors (see below), whose sum is σ = 65421408. Its totient is φ = 5627520.

The previous prime is 21103403. The next prime is 21103441. The reversal of 21103440 is 4430112.

It is a tau number, because it is divible by the number of its divisors (40).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21103441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43726 + ... + 44205.

Almost surely, 2^21103440 is an apocalyptic number.

21103440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21103440 is an abundant number, since it is smaller than the sum of its proper divisors (44317968).

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

21103440 is a wasteful number, since it uses less digits than its factorization.

21103440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87947 (or 87941 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21103440 is about 4593.8480601779. The cubic root of 21103440 is about 276.3446649761.

Adding to 21103440 its reverse (4430112), we get a palindrome (25533552).

The spelling of 21103440 in words is "twenty-one million, one hundred three thousand, four hundred forty".