28801981 has 4 divisors (see below), whose sum is σ = 31017532. Its totient is φ = 26586432.

The previous prime is 28801979. The next prime is 28802071. The reversal of 28801981 is 18910882.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18910882 = 2 ⋅9455441.

It can be written as a sum of positive squares in 2 ways, for example, as 1144900 + 27657081 = 1070^2 + 5259^2 .

It is a cyclic number.

It is not a de Polignac number, because 28801981 - 2¹ = 28801979 is a prime.

It is a super-2 number, since 2×28801981² = 1659108219048722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 28801981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28801951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1107756 + ... + 1107781.

It is an arithmetic number, because the mean of its divisors is an integer number (7754383).

Almost surely, 2^28801981 is an apocalyptic number.

It is an amenable number.

28801981 is a deficient number, since it is larger than the sum of its proper divisors (2215551).

28801981 is a wasteful number, since it uses less digits than its factorization.

28801981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2215550.

The product of its (nonzero) digits is 9216, while the sum is 37.

The square root of 28801981 is about 5366.7477116034. The cubic root of 28801981 is about 306.5308008471.

The spelling of 28801981 in words is "twenty-eight million, eight hundred one thousand, nine hundred eighty-one".