21281289 has 4 divisors (see below), whose sum is σ = 28375056. Its totient is φ = 14187524.

The previous prime is 21281261. The next prime is 21281321. The reversal of 21281289 is 98218212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21281289 - 2¹¹ = 21279241 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21281219) 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, 3546879 + ... + 3546884.

It is an arithmetic number, because the mean of its divisors is an integer number (7093764).

Almost surely, 2^21281289 is an apocalyptic number.

It is an amenable number.

21281289 is a deficient number, since it is larger than the sum of its proper divisors (7093767).

21281289 is an equidigital number, since it uses as much as digits as its factorization.

21281289 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7093766.

The product of its digits is 4608, while the sum is 33.

The square root of 21281289 is about 4613.1647488465. The cubic root of 21281289 is about 277.1187915552.

The spelling of 21281289 in words is "twenty-one million, two hundred eighty-one thousand, two hundred eighty-nine".