21525121 has 2 divisors, whose sum is σ = 21525122. Its totient is φ = 21525120.

The previous prime is 21525109. The next prime is 21525139. The reversal of 21525121 is 12152512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19044496 + 2480625 = 4364^2 + 1575^2 .

It is a cyclic number.

It is not a de Polignac number, because 21525121 - 2⁵ = 21525089 is a prime.

It is not a weakly prime, because it can be changed into another prime (21525151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10762560 + 10762561.

It is an arithmetic number, because the mean of its divisors is an integer number (10762561).

Almost surely, 2^21525121 is an apocalyptic number.

It is an amenable number.

21525121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21525121 is an equidigital number, since it uses as much as digits as its factorization.

21525121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 200, while the sum is 19.

The square root of 21525121 is about 4639.5173240327. The cubic root of 21525121 is about 278.1731449036.

Adding to 21525121 its reverse (12152512), we get a palindrome (33677633).

The spelling of 21525121 in words is "twenty-one million, five hundred twenty-five thousand, one hundred twenty-one".