21708428 has 24 divisors (see below), whose sum is σ = 43573152. Its totient is φ = 9270144.

The previous prime is 21708419. The next prime is 21708433. The reversal of 21708428 is 82480712.

It is a junction number, because it is equal to n+sod(n) for n = 21708394 and 21708403.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7526 + ... + 10002.

It is an arithmetic number, because the mean of its divisors is an integer number (1815548).

Almost surely, 2^21708428 is an apocalyptic number.

21708428 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21708428 is an abundant number, since it is smaller than the sum of its proper divisors (21864724).

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

21708428 is a wasteful number, since it uses less digits than its factorization.

21708428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2801 (or 2799 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 32.

The square root of 21708428 is about 4659.2304085546. The cubic root of 21708428 is about 278.9605507701.

The spelling of 21708428 in words is "twenty-one million, seven hundred eight thousand, four hundred twenty-eight".