28478981 has 4 divisors (see below), whose sum is σ = 28560012. Its totient is φ = 28397952.

The previous prime is 28478977. The next prime is 28479041. The reversal of 28478981 is 18987482.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18987482 = 2 ⋅9493741.

It can be written as a sum of positive squares in 2 ways, for example, as 7236100 + 21242881 = 2690^2 + 4609^2 .

It is a cyclic number.

It is not a de Polignac number, because 28478981 - 2² = 28478977 is a prime.

It is a super-2 number, since 2×28478981² = 1622104717596722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28478921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39986 + ... + 40691.

It is an arithmetic number, because the mean of its divisors is an integer number (7140003).

Almost surely, 2^28478981 is an apocalyptic number.

It is an amenable number.

28478981 is a deficient number, since it is larger than the sum of its proper divisors (81031).

28478981 is an equidigital number, since it uses as much as digits as its factorization.

28478981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81030.

The product of its digits is 258048, while the sum is 47.

The square root of 28478981 is about 5336.5701531977. The cubic root of 28478981 is about 305.3806266513.

The spelling of 28478981 in words is "twenty-eight million, four hundred seventy-eight thousand, nine hundred eighty-one".