21103840 has 24 divisors (see below), whose sum is σ = 49858200. Its totient is φ = 8441472.

The previous prime is 21103759. The next prime is 21103843. The reversal of 21103840 is 4830112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21103843) 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 3 ways as a sum of consecutive naturals, for example, 65790 + ... + 66109.

It is an arithmetic number, because the mean of its divisors is an integer number (2077425).

Almost surely, 2^21103840 is an apocalyptic number.

21103840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21103840 is an abundant number, since it is smaller than the sum of its proper divisors (28754360).

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

21103840 is a wasteful number, since it uses less digits than its factorization.

21103840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131914 (or 131906 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21103840 is about 4593.8915964572. The cubic root of 21103840 is about 276.3464109343.

Adding to 21103840 its reverse (4830112), we get a palindrome (25933952).

The spelling of 21103840 in words is "twenty-one million, one hundred three thousand, eight hundred forty".