28913881 has 4 divisors (see below), whose sum is σ = 28940752. Its totient is φ = 28887012.

The previous prime is 28913869. The next prime is 28913891. The reversal of 28913881 is 18831982.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28913881 - 2¹¹ = 28911833 is a prime.

It is a super-2 number, since 2×28913881² = 1672025028964322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28913831) 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 3 ways as a sum of consecutive naturals, for example, 11751 + ... + 13996.

It is an arithmetic number, because the mean of its divisors is an integer number (7235188).

Almost surely, 2^28913881 is an apocalyptic number.

It is an amenable number.

28913881 is a deficient number, since it is larger than the sum of its proper divisors (26871).

28913881 is a wasteful number, since it uses less digits than its factorization.

28913881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26870.

The product of its digits is 27648, while the sum is 40.

The square root of 28913881 is about 5377.1629136562. The cubic root of 28913881 is about 306.9272605097.

The spelling of 28913881 in words is "twenty-eight million, nine hundred thirteen thousand, eight hundred eighty-one".