28521139 has 2 divisors, whose sum is σ = 28521140. Its totient is φ = 28521138.

The previous prime is 28521137. The next prime is 28521149. The reversal of 28521139 is 93112582.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 28521139 - 2¹ = 28521137 is a prime.

Together with 28521137, it forms a pair of twin primes.

It is equal to p_1771861 and since 28521139 and 1771861 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28521139.

It is not a weakly prime, because it can be changed into another prime (28521137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14260569 + 14260570.

It is an arithmetic number, because the mean of its divisors is an integer number (14260570).

Almost surely, 2^28521139 is an apocalyptic number.

28521139 is a deficient number, since it is larger than the sum of its proper divisors (1).

28521139 is an equidigital number, since it uses as much as digits as its factorization.

28521139 is an evil number, because the sum of its binary digits is even.

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

The square root of 28521139 is about 5340.5186077758. The cubic root of 28521139 is about 305.5312393554.

The spelling of 28521139 in words is "twenty-eight million, five hundred twenty-one thousand, one hundred thirty-nine".