28009381 has 2 divisors, whose sum is σ = 28009382. Its totient is φ = 28009380.

The previous prime is 28009367. The next prime is 28009393. The reversal of 28009381 is 18390082.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27984100 + 25281 = 5290^2 + 159^2 .

It is a cyclic number.

It is not a de Polignac number, because 28009381 - 2¹⁹ = 27485093 is a prime.

It is a super-2 number, since 2×28009381² = 1569050848006322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28009301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14004690 + 14004691.

It is an arithmetic number, because the mean of its divisors is an integer number (14004691).

Almost surely, 2^28009381 is an apocalyptic number.

It is an amenable number.

28009381 is a deficient number, since it is larger than the sum of its proper divisors (1).

28009381 is an equidigital number, since it uses as much as digits as its factorization.

28009381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 28009381 is about 5292.3889690763. The cubic root of 28009381 is about 303.6928055928.

The spelling of 28009381 in words is "twenty-eight million, nine thousand, three hundred eighty-one".