28109561 has 2 divisors, whose sum is σ = 28109562. Its totient is φ = 28109560.

The previous prime is 28109537. The next prime is 28109579. The reversal of 28109561 is 16590182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 26584336 + 1525225 = 5156^2 + 1235^2 .

It is a cyclic number.

It is not a de Polignac number, because 28109561 - 2²² = 23915257 is a prime.

It is a super-2 number, since 2×28109561² = 1580294839225442, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (28109461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14054780 + 14054781.

It is an arithmetic number, because the mean of its divisors is an integer number (14054781).

Almost surely, 2^28109561 is an apocalyptic number.

It is an amenable number.

28109561 is a deficient number, since it is larger than the sum of its proper divisors (1).

28109561 is an equidigital number, since it uses as much as digits as its factorization.

28109561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 28109561 is about 5301.8450562045. The cubic root of 28109561 is about 304.0544433020.

The spelling of 28109561 in words is "twenty-eight million, one hundred nine thousand, five hundred sixty-one".