28121581 has 2 divisors, whose sum is σ = 28121582. Its totient is φ = 28121580.

The previous prime is 28121521. The next prime is 28121603. The reversal of 28121581 is 18512182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25593481 + 2528100 = 5059^2 + 1590^2 .

It is a cyclic number.

It is not a de Polignac number, because 28121581 - 2⁷ = 28121453 is a prime.

It is a super-2 number, since 2×28121581² = 1581646635879122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28121521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14060790 + 14060791.

It is an arithmetic number, because the mean of its divisors is an integer number (14060791).

Almost surely, 2^28121581 is an apocalyptic number.

It is an amenable number.

28121581 is a deficient number, since it is larger than the sum of its proper divisors (1).

28121581 is an equidigital number, since it uses as much as digits as its factorization.

28121581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1280, while the sum is 28.

The square root of 28121581 is about 5302.9785026907. The cubic root of 28121581 is about 304.0977762875.

The spelling of 28121581 in words is "twenty-eight million, one hundred twenty-one thousand, five hundred eighty-one".