21438989 has 16 divisors (see below), whose sum is σ = 26671680. Its totient is φ = 16930560.

The previous prime is 21438961. The next prime is 21439079. The reversal of 21438989 is 98983412.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21438989 - 2⁸ = 21438733 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438089) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1979 + ... + 6840.

It is an arithmetic number, because the mean of its divisors is an integer number (1666980).

Almost surely, 2^21438989 is an apocalyptic number.

It is an amenable number.

21438989 is a deficient number, since it is larger than the sum of its proper divisors (5232691).

21438989 is a wasteful number, since it uses less digits than its factorization.

21438989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8860.

The product of its digits is 124416, while the sum is 44.

The square root of 21438989 is about 4630.2255884568. The cubic root of 21438989 is about 277.8016156195.

The spelling of 21438989 in words is "twenty-one million, four hundred thirty-eight thousand, nine hundred eighty-nine".