28717821 has 40 divisors (see below), whose sum is σ = 47323584. Its totient is φ = 17210880.

The previous prime is 28717807. The next prime is 28717847. The reversal of 28717821 is 12871782.

It is a happy number.

It is not a de Polignac number, because 28717821 - 2⁶ = 28717757 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28717861) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 148701 + ... + 148893.

Almost surely, 2^28717821 is an apocalyptic number.

It is an amenable number.

28717821 is a deficient number, since it is larger than the sum of its proper divisors (18605763).

28717821 is a wasteful number, since it uses less digits than its factorization.

28717821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383 (or 374 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 28717821 is about 5358.9011000391. The cubic root of 28717821 is about 306.2319464021.

The spelling of 28717821 in words is "twenty-eight million, seven hundred seventeen thousand, eight hundred twenty-one".