21280289 has 2 divisors, whose sum is σ = 21280290. Its totient is φ = 21280288.

The previous prime is 21280261. The next prime is 21280307. The reversal of 21280289 is 98208212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 258064 = 4585^2 + 508^2 .

It is a cyclic number.

It is not a de Polignac number, because 21280289 - 2¹² = 21276193 is a prime.

It is not a weakly prime, because it can be changed into another prime (21280219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10640144 + 10640145.

It is an arithmetic number, because the mean of its divisors is an integer number (10640145).

Almost surely, 2^21280289 is an apocalyptic number.

It is an amenable number.

21280289 is a deficient number, since it is larger than the sum of its proper divisors (1).

21280289 is an equidigital number, since it uses as much as digits as its factorization.

21280289 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21280289 is about 4613.0563621096. The cubic root of 21280289 is about 277.1144509170.

The spelling of 21280289 in words is "twenty-one million, two hundred eighty thousand, two hundred eighty-nine".