21251525 has 6 divisors (see below), whose sum is σ = 26351922. Its totient is φ = 17001200.

The previous prime is 21251491. The next prime is 21251533. The reversal of 21251525 is 52515212.

It can be written as a sum of positive squares in 3 ways, for example, as 146689 + 21104836 = 383^2 + 4594^2 .

It is not a de Polignac number, because 21251525 - 2²² = 17057221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21251525.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 425006 + ... + 425055.

It is an arithmetic number, because the mean of its divisors is an integer number (4391987).

Almost surely, 2^21251525 is an apocalyptic number.

21251525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21251525 is a deficient number, since it is larger than the sum of its proper divisors (5100397).

21251525 is an equidigital number, since it uses as much as digits as its factorization.

21251525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 850071 (or 850066 counting only the distinct ones).

The product of its digits is 1000, while the sum is 23.

The square root of 21251525 is about 4609.9376351530. The cubic root of 21251525 is about 276.9895385450.

Adding to 21251525 its reverse (52515212), we get a palindrome (73766737).

The spelling of 21251525 in words is "twenty-one million, two hundred fifty-one thousand, five hundred twenty-five".