28117821 has 8 divisors (see below), whose sum is σ = 37612224. Its totient is φ = 18684320.

The previous prime is 28117819. The next prime is 28117871. The reversal of 28117821 is 12871182.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 28117821 - 2¹ = 28117819 is a prime.

It is a super-2 number, since 2×28117821² = 1581223715576082, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28117801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14136 + ... + 16001.

It is an arithmetic number, because the mean of its divisors is an integer number (4701528).

Almost surely, 2^28117821 is an apocalyptic number.

It is an amenable number.

28117821 is a deficient number, since it is larger than the sum of its proper divisors (9494403).

28117821 is a wasteful number, since it uses less digits than its factorization.

28117821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30451.

The product of its digits is 1792, while the sum is 30.

The square root of 28117821 is about 5302.6239730911. The cubic root of 28117821 is about 304.0842225379.

The spelling of 28117821 in words is "twenty-eight million, one hundred seventeen thousand, eight hundred twenty-one".