21209489 has 8 divisors (see below), whose sum is σ = 25665408. Its totient is φ = 17110080.

The previous prime is 21209471. The next prime is 21209537. The reversal of 21209489 is 98490212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21209489 is a prime.

It is a super-2 number, since 2×21209489² = 899684847282242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21209429) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 88997 + ... + 89234.

It is an arithmetic number, because the mean of its divisors is an integer number (3208176).

Almost surely, 2^21209489 is an apocalyptic number.

It is an amenable number.

21209489 is a deficient number, since it is larger than the sum of its proper divisors (4455919).

21209489 is a wasteful number, since it uses less digits than its factorization.

21209489 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178255.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 21209489 is about 4605.3760975625. The cubic root of 21209489 is about 276.8067874601.

The spelling of 21209489 in words is "twenty-one million, two hundred nine thousand, four hundred eighty-nine".