28212321 has 16 divisors (see below), whose sum is σ = 39839040. Its totient is φ = 17709120.

The previous prime is 28212311. The next prime is 28212323. The reversal of 28212321 is 12321282.

It is a happy number.

It is not a de Polignac number, because 28212321 - 2¹⁸ = 27950177 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28212323) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8431 + ... + 11291.

It is an arithmetic number, because the mean of its divisors is an integer number (2489940).

Almost surely, 2^28212321 is an apocalyptic number.

It is an amenable number.

28212321 is a deficient number, since it is larger than the sum of its proper divisors (11626719).

28212321 is a wasteful number, since it uses less digits than its factorization.

28212321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3056.

The product of its digits is 384, while the sum is 21.

The square root of 28212321 is about 5311.5271815176. The cubic root of 28212321 is about 304.4245028950.

The spelling of 28212321 in words is "twenty-eight million, two hundred twelve thousand, three hundred twenty-one".