28331781 has 8 divisors (see below), whose sum is σ = 38129184. Its totient is φ = 18711120.

The previous prime is 28331767. The next prime is 28331783. The reversal of 28331781 is 18713382.

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

It is not a de Polignac number, because 28331781 - 2²³ = 19943173 is a prime.

It is a super-2 number, since 2×28331781² = 1605379629263922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28331783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43810 + ... + 44451.

It is an arithmetic number, because the mean of its divisors is an integer number (4766148).

Almost surely, 2^28331781 is an apocalyptic number.

It is an amenable number.

28331781 is a deficient number, since it is larger than the sum of its proper divisors (9797403).

28331781 is a wasteful number, since it uses less digits than its factorization.

28331781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 88371.

The product of its digits is 8064, while the sum is 33.

The square root of 28331781 is about 5322.7606559003. The cubic root of 28331781 is about 304.8535747925.

The spelling of 28331781 in words is "twenty-eight million, three hundred thirty-one thousand, seven hundred eighty-one".