28139218 has 4 divisors (see below), whose sum is σ = 42208830. Its totient is φ = 14069608.

The previous prime is 28139201. The next prime is 28139249. The reversal of 28139218 is 81293182.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81293182 = 2 ⋅40646591.

It can be written as a sum of positive squares in only one way, i.e., 22724289 + 5414929 = 4767^2 + 2327^2 .

It is a super-3 number, since 3×28139218³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7034803 + ... + 7034806.

Almost surely, 2^28139218 is an apocalyptic number.

28139218 is a deficient number, since it is larger than the sum of its proper divisors (14069612).

28139218 is a wasteful number, since it uses less digits than its factorization.

28139218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14069611.

The product of its digits is 6912, while the sum is 34.

The square root of 28139218 is about 5304.6411754236. The cubic root of 28139218 is about 304.1613366260.

The spelling of 28139218 in words is "twenty-eight million, one hundred thirty-nine thousand, two hundred eighteen".