28909381 has 2 divisors, whose sum is σ = 28909382. Its totient is φ = 28909380.

The previous prime is 28909379. The next prime is 28909399. The reversal of 28909381 is 18390982.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28037025 + 872356 = 5295^2 + 934^2 .

It is a cyclic number.

It is not a de Polignac number, because 28909381 - 2¹ = 28909379 is a prime.

It is a super-2 number, since 2×28909381² = 1671504619606322, which contains 22 as substring.

Together with 28909379, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28909301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14454690 + 14454691.

It is an arithmetic number, because the mean of its divisors is an integer number (14454691).

Almost surely, 2^28909381 is an apocalyptic number.

It is an amenable number.

28909381 is a deficient number, since it is larger than the sum of its proper divisors (1).

28909381 is an equidigital number, since it uses as much as digits as its factorization.

28909381 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 28909381 is about 5376.7444611028. The cubic root of 28909381 is about 306.9113368509.

The spelling of 28909381 in words is "twenty-eight million, nine hundred nine thousand, three hundred eighty-one".