28949781 has 8 divisors (see below), whose sum is σ = 44113984. Its totient is φ = 16542720.

The previous prime is 28949779. The next prime is 28949857. The reversal of 28949781 is 18794982.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 28949781 - 2¹ = 28949779 is a prime.

It is a super-2 number, since 2×28949781² = 1676179639895922, which contains 22 as substring.

It is the 5381-st Hogben number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28949781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28949761) by changing a digit.

It is a nontrivial repunit in base 5380.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 689260 + ... + 689301.

It is an arithmetic number, because the mean of its divisors is an integer number (5514248).

Almost surely, 2^28949781 is an apocalyptic number.

28949781 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28949781 is a deficient number, since it is larger than the sum of its proper divisors (15164203).

28949781 is a wasteful number, since it uses less digits than its factorization.

28949781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1378571.

The product of its digits is 290304, while the sum is 48.

The square root of 28949781 is about 5380.5000696961. The cubic root of 28949781 is about 307.0542367933.

The spelling of 28949781 in words is "twenty-eight million, nine hundred forty-nine thousand, seven hundred eighty-one".