21605125 has 16 divisors (see below), whose sum is σ = 27099072. Its totient is φ = 17197200.

The previous prime is 21605123. The next prime is 21605159. The reversal of 21605125 is 52150612.

It is not a de Polignac number, because 21605125 - 2¹ = 21605123 is a prime.

It is a super-3 number, since 3×21605125³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21605096 and 21605105.

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

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38094 + ... + 38656.

It is an arithmetic number, because the mean of its divisors is an integer number (1693692).

Almost surely, 2^21605125 is an apocalyptic number.

21605125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21605125 is a deficient number, since it is larger than the sum of its proper divisors (5493947).

21605125 is an equidigital number, since it uses as much as digits as its factorization.

21605125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 885 (or 875 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 22.

The square root of 21605125 is about 4648.1313449600. The cubic root of 21605125 is about 278.5173543331.

Adding to 21605125 its reverse (52150612), we get a palindrome (73755737).

The spelling of 21605125 in words is "twenty-one million, six hundred five thousand, one hundred twenty-five".