28631681 has 4 divisors (see below), whose sum is σ = 30834132. Its totient is φ = 26429232.

The previous prime is 28631663. The next prime is 28631717. The reversal of 28631681 is 18613682.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18613682 = 2 ⋅9306841.

It can be written as a sum of positive squares in 2 ways, for example, as 10857025 + 17774656 = 3295^2 + 4216^2 .

It is a cyclic number.

It is not a de Polignac number, because 28631681 - 2¹⁴ = 28615297 is a prime.

It is a super-2 number, since 2×28631681² = 1639546313771522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28631881) 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, 1101206 + ... + 1101231.

It is an arithmetic number, because the mean of its divisors is an integer number (7708533).

Almost surely, 2^28631681 is an apocalyptic number.

It is an amenable number.

28631681 is a deficient number, since it is larger than the sum of its proper divisors (2202451).

28631681 is a wasteful number, since it uses less digits than its factorization.

28631681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2202450.

The product of its digits is 13824, while the sum is 35.

The square root of 28631681 is about 5350.8579685878. The cubic root of 28631681 is about 305.9254556624.

The spelling of 28631681 in words is "twenty-eight million, six hundred thirty-one thousand, six hundred eighty-one".