28039981 has 2 divisors, whose sum is σ = 28039982. Its totient is φ = 28039980.

The previous prime is 28039961. The next prime is 28039993. The reversal of 28039981 is 18993082.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27562500 + 477481 = 5250^2 + 691^2 .

It is a cyclic number.

It is not a de Polignac number, because 28039981 - 2⁷ = 28039853 is a prime.

It is a super-2 number, since 2×28039981² = 1572481068960722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28039951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14019990 + 14019991.

It is an arithmetic number, because the mean of its divisors is an integer number (14019991).

Almost surely, 2^28039981 is an apocalyptic number.

It is an amenable number.

28039981 is a deficient number, since it is larger than the sum of its proper divisors (1).

28039981 is an equidigital number, since it uses as much as digits as its factorization.

28039981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 28039981 is about 5295.2791238989. The cubic root of 28039981 is about 303.8033592407.

The spelling of 28039981 in words is "twenty-eight million, thirty-nine thousand, nine hundred eighty-one".