21653125 has 36 divisors (see below), whose sum is σ = 30021516. Its totient is φ = 15600000.

The previous prime is 21653101. The next prime is 21653129. The reversal of 21653125 is 52135612.

21653125 is nontrivially palindromic in base 4.

It can be written as a sum of positive squares in 18 ways, for example, as 5788836 + 15864289 = 2406^2 + 3983^2 .

It is not a de Polignac number, because 21653125 - 2⁷ = 21652997 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21653125.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21653129) 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 35 ways as a sum of consecutive naturals, for example, 528105 + ... + 528145.

It is an arithmetic number, because the mean of its divisors is an integer number (833931).

Almost surely, 2^21653125 is an apocalyptic number.

21653125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21653125 is a deficient number, since it is larger than the sum of its proper divisors (8368391).

21653125 is an frugal number, since it uses more digits than its factorization.

21653125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92 (or 59 counting only the distinct ones).

The product of its digits is 1800, while the sum is 25.

The square root of 21653125 is about 4653.2918455648. The cubic root of 21653125 is about 278.7234619845.

Adding to 21653125 its reverse (52135612), we get a palindrome (73788737).

The spelling of 21653125 in words is "twenty-one million, six hundred fifty-three thousand, one hundred twenty-five".