21530125 has 16 divisors (see below), whose sum is σ = 27531504. Its totient is φ = 16800000.

The previous prime is 21530123. The next prime is 21530129. The reversal of 21530125 is 52103512.

It can be written as a sum of positive squares in 8 ways, for example, as 18096516 + 3433609 = 4254^2 + 1853^2 .

It is not a de Polignac number, because 21530125 - 2¹ = 21530123 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21530123) 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, 3025 + ... + 7225.

It is an arithmetic number, because the mean of its divisors is an integer number (1720719).

Almost surely, 2^21530125 is an apocalyptic number.

21530125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21530125 is a deficient number, since it is larger than the sum of its proper divisors (6001379).

21530125 is an equidigital number, since it uses as much as digits as its factorization.

21530125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4257 (or 4247 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21530125 is about 4640.0565729310. The cubic root of 21530125 is about 278.1946991079.

Adding to 21530125 its reverse (52103512), we get a palindrome (73633637).

The spelling of 21530125 in words is "twenty-one million, five hundred thirty thousand, one hundred twenty-five".