28201681 has 6 divisors (see below), whose sum is σ = 29764482. Its totient is φ = 26717040.

The previous prime is 28201673. The next prime is 28201687. The reversal of 28201681 is 18610282.

It can be written as a sum of positive squares in only one way, i.e., 24591681 + 3610000 = 4959^2 + 1900^2 .

It is not a de Polignac number, because 28201681 - 2³ = 28201673 is a prime.

It is a super-2 number, since 2×28201681² = 1590669622451522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28201687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 38700 + ... + 39421.

It is an arithmetic number, because the mean of its divisors is an integer number (4960747).

Almost surely, 2^28201681 is an apocalyptic number.

It is an amenable number.

28201681 is a deficient number, since it is larger than the sum of its proper divisors (1562801).

28201681 is an equidigital number, since it uses as much as digits as its factorization.

28201681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78159 (or 78140 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 28201681 is about 5310.5254918887. The cubic root of 28201681 is about 304.3862278450.

It can be divided in two parts, 28201 and 681, that added together give a palindrome (28882).

The spelling of 28201681 in words is "twenty-eight million, two hundred one thousand, six hundred eighty-one".