28201181 has 4 divisors (see below), whose sum is σ = 29860092. Its totient is φ = 26542272.

The previous prime is 28201087. The next prime is 28201189. The reversal of 28201181 is 18110282.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18110282 = 2 ⋅9055141.

It can be written as a sum of positive squares in 2 ways, for example, as 8797156 + 19404025 = 2966^2 + 4405^2 .

It is a cyclic number.

It is not a de Polignac number, because 28201181 - 2¹⁰ = 28200157 is a prime.

It is a super-2 number, since 2×28201181² = 1590613219589522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28201189) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 829430 + ... + 829463.

It is an arithmetic number, because the mean of its divisors is an integer number (7465023).

Almost surely, 2^28201181 is an apocalyptic number.

It is an amenable number.

28201181 is a deficient number, since it is larger than the sum of its proper divisors (1658911).

28201181 is a wasteful number, since it uses less digits than its factorization.

28201181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1658910.

The product of its (nonzero) digits is 256, while the sum is 23.

The square root of 28201181 is about 5310.4784153596. The cubic root of 28201181 is about 304.3844289686.

It can be divided in two parts, 28201 and 181, that added together give a palindrome (28382).

The spelling of 28201181 in words is "twenty-eight million, two hundred one thousand, one hundred eighty-one".