21103684 has 48 divisors (see below), whose sum is σ = 44706816. Its totient is φ = 8524800.

The previous prime is 21103679. The next prime is 21103697. The reversal of 21103684 is 48630112.

21103684 = T₁₈₂ + T₁₈₃ + ... + T₅₀₉.

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, 35292 + ... + 35884.

It is an arithmetic number, because the mean of its divisors is an integer number (931392).

Almost surely, 2^21103684 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21103684, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22353408).

21103684 is an abundant number, since it is smaller than the sum of its proper divisors (23603132).

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

21103684 is a wasteful number, since it uses less digits than its factorization.

21103684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 676 (or 674 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21103684 is about 4593.8746173573. The cubic root of 21103684 is about 276.3457300132.

Adding to 21103684 its product of nonzero digits (1152), we get a square (21104836 = 4594²).

Adding to 21103684 its reverse (48630112), we get a palindrome (69733796).

The spelling of 21103684 in words is "twenty-one million, one hundred three thousand, six hundred eighty-four".