21528139 has 2 divisors, whose sum is σ = 21528140. Its totient is φ = 21528138.

The previous prime is 21528131. The next prime is 21528149. The reversal of 21528139 is 93182512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21528139 - 2³ = 21528131 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21528139.

It is not a weakly prime, because it can be changed into another prime (21528131) 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, 10764069 + 10764070.

It is an arithmetic number, because the mean of its divisors is an integer number (10764070).

Almost surely, 2^21528139 is an apocalyptic number.

21528139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21528139 is an equidigital number, since it uses as much as digits as its factorization.

21528139 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 21528139 is about 4639.8425619842. The cubic root of 21528139 is about 278.1861450213.

The spelling of 21528139 in words is "twenty-one million, five hundred twenty-eight thousand, one hundred thirty-nine".