21525145 has 16 divisors (see below), whose sum is σ = 27732240. Its totient is φ = 15980544.

The previous prime is 21525139. The next prime is 21525151. The reversal of 21525145 is 54152512.

It is an interprime number because it is at equal distance from previous prime (21525139) and next prime (21525151).

It can be written as a sum of positive squares in 8 ways, for example, as 831744 + 20693401 = 912^2 + 4549^2 .

It is not a de Polignac number, because 21525145 - 2⁷ = 21525017 is a prime.

It is an unprimeable number.

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, 4471 + ... + 7939.

It is an arithmetic number, because the mean of its divisors is an integer number (1733265).

Almost surely, 2^21525145 is an apocalyptic number.

It is an amenable number.

21525145 is a deficient number, since it is larger than the sum of its proper divisors (6207095).

21525145 is a wasteful number, since it uses less digits than its factorization.

21525145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3564.

The product of its digits is 2000, while the sum is 25.

The square root of 21525145 is about 4639.5199105080. The cubic root of 21525145 is about 278.1732482891.

Adding to 21525145 its reverse (54152512), we get a palindrome (75677657).

It can be divided in two parts, 215251 and 45, that added together give a square (215296 = 464²).

The spelling of 21525145 in words is "twenty-one million, five hundred twenty-five thousand, one hundred forty-five".