21105125 has 16 divisors (see below), whose sum is σ = 26598000. Its totient is φ = 16718400.

The previous prime is 21105121. The next prime is 21105169. The reversal of 21105125 is 52150112.

It can be written as a sum of positive squares in 8 ways, for example, as 6466849 + 14638276 = 2543^2 + 3826^2 .

It is not a de Polignac number, because 21105125 - 2² = 21105121 is a prime.

It is a super-3 number, since 3×21105125³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12851 + ... + 14399.

It is an arithmetic number, because the mean of its divisors is an integer number (1662375).

Almost surely, 2^21105125 is an apocalyptic number.

21105125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21105125 is a deficient number, since it is larger than the sum of its proper divisors (5492875).

21105125 is a wasteful number, since it uses less digits than its factorization.

21105125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1673 (or 1663 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21105125 is about 4594.0314539628. The cubic root of 21105125 is about 276.3520196755.

Adding to 21105125 its reverse (52150112), we get a palindrome (73255237).

The spelling of 21105125 in words is "twenty-one million, one hundred five thousand, one hundred twenty-five".