21103940 has 96 divisors (see below), whose sum is σ = 53512704. Its totient is φ = 6888960.

The previous prime is 21103937. The next prime is 21103961. The reversal of 21103940 is 4930112.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 134342 + ... + 134498.

It is an arithmetic number, because the mean of its divisors is an integer number (557424).

Almost surely, 2^21103940 is an apocalyptic number.

21103940 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 21103940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26756352).

21103940 is an abundant number, since it is smaller than the sum of its proper divisors (32408764).

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

21103940 is a wasteful number, since it uses less digits than its factorization.

21103940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237 (or 235 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21103940 is about 4593.9024804626. The cubic root of 21103940 is about 276.3468474204.

Subtracting from 21103940 its reverse (4930112), we obtain a triangular number (16173828 = T₅₆₈₇).

The spelling of 21103940 in words is "twenty-one million, one hundred three thousand, nine hundred forty".