28005661 has 2 divisors, whose sum is σ = 28005662. Its totient is φ = 28005660.

The previous prime is 28005641. The next prime is 28005667. The reversal of 28005661 is 16650082.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20748025 + 7257636 = 4555^2 + 2694^2 .

It is a cyclic number.

It is not a de Polignac number, because 28005661 - 2⁵ = 28005629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28005667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14002830 + 14002831.

It is an arithmetic number, because the mean of its divisors is an integer number (14002831).

Almost surely, 2^28005661 is an apocalyptic number.

It is an amenable number.

28005661 is a deficient number, since it is larger than the sum of its proper divisors (1).

28005661 is an equidigital number, since it uses as much as digits as its factorization.

28005661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 28005661 is about 5292.0375093153. The cubic root of 28005661 is about 303.6793602492.

The spelling of 28005661 in words is "twenty-eight million, five thousand, six hundred sixty-one".