21217489 has 4 divisors (see below), whose sum is σ = 21436324. Its totient is φ = 20998656.

The previous prime is 21217481. The next prime is 21217499. The reversal of 21217489 is 98471212.

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 6838225 + 14379264 = 2615^2 + 3792^2 .

It is a cyclic number.

It is not a de Polignac number, because 21217489 - 2³ = 21217481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21217481) 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, 109272 + ... + 109465.

It is an arithmetic number, because the mean of its divisors is an integer number (5359081).

Almost surely, 2^21217489 is an apocalyptic number.

It is an amenable number.

21217489 is a deficient number, since it is larger than the sum of its proper divisors (218835).

21217489 is an equidigital number, since it uses as much as digits as its factorization.

21217489 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218834.

The product of its digits is 8064, while the sum is 34.

The square root of 21217489 is about 4606.2445658041. The cubic root of 21217489 is about 276.8415859715.

The spelling of 21217489 in words is "twenty-one million, two hundred seventeen thousand, four hundred eighty-nine".