28143981 has 6 divisors (see below), whose sum is σ = 40652430. Its totient is φ = 18762648.

The previous prime is 28143971. The next prime is 28144033. The reversal of 28143981 is 18934182.

It can be written as a sum of positive squares in only one way, i.e., 21206025 + 6937956 = 4605^2 + 2634^2 .

It is not a de Polignac number, because 28143981 - 2¹⁹ = 27619693 is a prime.

It is a super-2 number, since 2×28143981² = 1584167333056722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28143911) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1563546 + ... + 1563563.

It is an arithmetic number, because the mean of its divisors is an integer number (6775405).

Almost surely, 2^28143981 is an apocalyptic number.

It is an amenable number.

28143981 is a deficient number, since it is larger than the sum of its proper divisors (12508449).

28143981 is a wasteful number, since it uses less digits than its factorization.

28143981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3127115 (or 3127112 counting only the distinct ones).

The product of its digits is 13824, while the sum is 36.

The square root of 28143981 is about 5305.0901029106. The cubic root of 28143981 is about 304.1784970024.

The spelling of 28143981 in words is "twenty-eight million, one hundred forty-three thousand, nine hundred eighty-one".