21173620 has 96 divisors (see below), whose sum is σ = 51480576. Its totient is φ = 7257600.

The previous prime is 21173611. The next prime is 21173623. The reversal of 21173620 is 2637112.

It is a junction number, because it is equal to n+sod(n) for n = 21173591 and 21173600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21173623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 298185 + ... + 298255.

It is an arithmetic number, because the mean of its divisors is an integer number (536256).

Almost surely, 2^21173620 is an apocalyptic number.

21173620 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 21173620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25740288).

21173620 is an abundant number, since it is smaller than the sum of its proper divisors (30306956).

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

21173620 is a wasteful number, since it uses less digits than its factorization.

21173620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161 (or 159 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21173620 is about 4601.4801966324. The cubic root of 21173620 is about 276.6506563210.

The spelling of 21173620 in words is "twenty-one million, one hundred seventy-three thousand, six hundred twenty".