21528769 has 2 divisors, whose sum is σ = 21528770. Its totient is φ = 21528768.

The previous prime is 21528743. The next prime is 21528779. The reversal of 21528769 is 96782512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15303744 + 6225025 = 3912^2 + 2495^2 .

It is a cyclic number.

It is not a de Polignac number, because 21528769 - 2⁹ = 21528257 is a prime.

It is a super-2 number, since 2×21528769² = 926975789310722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21528739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10764384 + 10764385.

It is an arithmetic number, because the mean of its divisors is an integer number (10764385).

Almost surely, 2^21528769 is an apocalyptic number.

It is an amenable number.

21528769 is a deficient number, since it is larger than the sum of its proper divisors (1).

21528769 is an equidigital number, since it uses as much as digits as its factorization.

21528769 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 40.

The square root of 21528769 is about 4639.9104517221. The cubic root of 21528769 is about 278.1888586103.

The spelling of 21528769 in words is "twenty-one million, five hundred twenty-eight thousand, seven hundred sixty-nine".