21528389 has 2 divisors, whose sum is σ = 21528390. Its totient is φ = 21528388.

The previous prime is 21528383. The next prime is 21528433. The reversal of 21528389 is 98382512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19651489 + 1876900 = 4433^2 + 1370^2 .

It is a cyclic number.

It is not a de Polignac number, because 21528389 - 2²⁰ = 20479813 is a prime.

It is a super-3 number, since 3×21528389³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21528383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10764194 + 10764195.

It is an arithmetic number, because the mean of its divisors is an integer number (10764195).

Almost surely, 2^21528389 is an apocalyptic number.

It is an amenable number.

21528389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21528389 is an equidigital number, since it uses as much as digits as its factorization.

21528389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34560, while the sum is 38.

The square root of 21528389 is about 4639.8695024753. The cubic root of 21528389 is about 278.1872218486.

The spelling of 21528389 in words is "twenty-one million, five hundred twenty-eight thousand, three hundred eighty-nine".