28809781 has 32 divisors (see below), whose sum is σ = 40981248. Its totient is φ = 19491840.

The previous prime is 28809779. The next prime is 28809817. The reversal of 28809781 is 18790882.

It is a cyclic number.

It is not a de Polignac number, because 28809781 - 2¹ = 28809779 is a prime.

It is a super-2 number, since 2×28809781² = 1660006962535922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28809701) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 16171 + ... + 17863.

It is an arithmetic number, because the mean of its divisors is an integer number (1280664).

Almost surely, 2^28809781 is an apocalyptic number.

It is an amenable number.

28809781 is a deficient number, since it is larger than the sum of its proper divisors (12171467).

28809781 is a wasteful number, since it uses less digits than its factorization.

28809781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1741.

The product of its (nonzero) digits is 64512, while the sum is 43.

The square root of 28809781 is about 5367.4743595103. The cubic root of 28809781 is about 306.5584693658.

The spelling of 28809781 in words is "twenty-eight million, eight hundred nine thousand, seven hundred eighty-one".