21605120 has 36 divisors (see below), whose sum is σ = 51754080. Its totient is φ = 8641536.

The previous prime is 21605117. The next prime is 21605123. The reversal of 21605120 is 2150612.

It is an interprime number because it is at equal distance from previous prime (21605117) and next prime (21605123).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605123) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7160 + ... + 9719.

Almost surely, 2^21605120 is an apocalyptic number.

21605120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21605120 is an abundant number, since it is smaller than the sum of its proper divisors (30148960).

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

21605120 is an equidigital number, since it uses as much as digits as its factorization.

21605120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16900 (or 16886 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21605120 is about 4648.1308071095. The cubic root of 21605120 is about 278.5173328476.

Adding to 21605120 its reverse (2150612), we get a palindrome (23755732).

The spelling of 21605120 in words is "twenty-one million, six hundred five thousand, one hundred twenty".