28721269 has 4 divisors (see below), whose sum is σ = 29005740. Its totient is φ = 28436800.

The previous prime is 28721267. The next prime is 28721309. The reversal of 28721269 is 96212782.

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

It can be written as a sum of positive squares in 2 ways, for example, as 21762225 + 6959044 = 4665^2 + 2638^2 .

It is a cyclic number.

It is not a de Polignac number, because 28721269 - 2¹ = 28721267 is a prime.

It is a super-2 number, since 2×28721269² = 1649822585940722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28721267) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 142084 + ... + 142285.

It is an arithmetic number, because the mean of its divisors is an integer number (7251435).

Almost surely, 2^28721269 is an apocalyptic number.

It is an amenable number.

28721269 is a deficient number, since it is larger than the sum of its proper divisors (284471).

28721269 is a wasteful number, since it uses less digits than its factorization.

28721269 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284470.

The product of its digits is 24192, while the sum is 37.

The square root of 28721269 is about 5359.2227981303. Note that the first 3 decimals coincide. The cubic root of 28721269 is about 306.2442018061.

The spelling of 28721269 in words is "twenty-eight million, seven hundred twenty-one thousand, two hundred sixty-nine".