28971521 has 2 divisors, whose sum is σ = 28971522. Its totient is φ = 28971520.

The previous prime is 28971517. The next prime is 28971529. The reversal of 28971521 is 12517982.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23658496 + 5313025 = 4864^2 + 2305^2 .

It is a cyclic number.

It is not a de Polignac number, because 28971521 - 2² = 28971517 is a prime.

It is not a weakly prime, because it can be changed into another prime (28971529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14485760 + 14485761.

It is an arithmetic number, because the mean of its divisors is an integer number (14485761).

Almost surely, 2^28971521 is an apocalyptic number.

It is an amenable number.

28971521 is a deficient number, since it is larger than the sum of its proper divisors (1).

28971521 is an equidigital number, since it uses as much as digits as its factorization.

28971521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10080, while the sum is 35.

The square root of 28971521 is about 5382.5199488715. The cubic root of 28971521 is about 307.1310789272.

It can be divided in two parts, 28971 and 521, that added together give a palindrome (29492).

The spelling of 28971521 in words is "twenty-eight million, nine hundred seventy-one thousand, five hundred twenty-one".