28280781 has 6 divisors (see below), whose sum is σ = 40850030. Its totient is φ = 18853848.

The previous prime is 28280779. The next prime is 28280783. The reversal of 28280781 is 18708282.

It is an interprime number because it is at equal distance from previous prime (28280779) and next prime (28280783).

It can be written as a sum of positive squares in only one way, i.e., 28196100 + 84681 = 5310^2 + 291^2 .

It is not a de Polignac number, because 28280781 - 2¹ = 28280779 is a prime.

It is a super-2 number, since 2×28280781² = 1599605147939922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28280783) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1571146 + ... + 1571163.

Almost surely, 2^28280781 is an apocalyptic number.

It is an amenable number.

28280781 is a deficient number, since it is larger than the sum of its proper divisors (12569249).

28280781 is a wasteful number, since it uses less digits than its factorization.

28280781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3142315 (or 3142312 counting only the distinct ones).

The product of its (nonzero) digits is 14336, while the sum is 36.

The square root of 28280781 is about 5317.9677509364. The cubic root of 28280781 is about 304.6705427565.

The spelling of 28280781 in words is "twenty-eight million, two hundred eighty thousand, seven hundred eighty-one".