28221951 has 4 divisors (see below), whose sum is σ = 37629272. Its totient is φ = 18814632.

The previous prime is 28221937. The next prime is 28221961. The reversal of 28221951 is 15912282.

It is a semiprime because it is the product of two primes.

It is a de Polignac number, because none of the positive numbers 2^k-28221951 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28221911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4703656 + ... + 4703661.

It is an arithmetic number, because the mean of its divisors is an integer number (9407318).

Almost surely, 2^28221951 is an apocalyptic number.

28221951 is a deficient number, since it is larger than the sum of its proper divisors (9407321).

28221951 is an equidigital number, since it uses as much as digits as its factorization.

28221951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9407320.

The product of its digits is 2880, while the sum is 30.

The square root of 28221951 is about 5312.4336231147. The cubic root of 28221951 is about 304.4591363975.

The spelling of 28221951 in words is "twenty-eight million, two hundred twenty-one thousand, nine hundred fifty-one".