28688021 has 2 divisors, whose sum is σ = 28688022. Its totient is φ = 28688020.

The previous prime is 28688017. The next prime is 28688053. The reversal of 28688021 is 12088682.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27984100 + 703921 = 5290^2 + 839^2 .

It is a cyclic number.

It is not a de Polignac number, because 28688021 - 2² = 28688017 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28688321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14344010 + 14344011.

It is an arithmetic number, because the mean of its divisors is an integer number (14344011).

Almost surely, 2^28688021 is an apocalyptic number.

It is an amenable number.

28688021 is a deficient number, since it is larger than the sum of its proper divisors (1).

28688021 is an equidigital number, since it uses as much as digits as its factorization.

28688021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12288, while the sum is 35.

The square root of 28688021 is about 5356.1199575812. The cubic root of 28688021 is about 306.1259858285.

The spelling of 28688021 in words is "twenty-eight million, six hundred eighty-eight thousand, twenty-one".