21042608 has 40 divisors (see below), whose sum is σ = 42902016. Its totient is φ = 9979200.

The previous prime is 21042601. The next prime is 21042629. The reversal of 21042608 is 80624012.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77513 + ... + 77783.

Almost surely, 2^21042608 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 21042608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21451008).

21042608 is an abundant number, since it is smaller than the sum of its proper divisors (21859408).

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

21042608 is a wasteful number, since it uses less digits than its factorization.

21042608 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 513 (or 507 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21042608 is about 4587.2222531724. Note that the first 4 decimals coincide. The cubic root of 21042608 is about 276.0788824447.

The spelling of 21042608 in words is "twenty-one million, forty-two thousand, six hundred eight".