21408989 has 16 divisors (see below), whose sum is σ = 25470720. Its totient is φ = 17606400.

The previous prime is 21408983. The next prime is 21409009. The reversal of 21408989 is 98980412.

21408989 is nontrivially palindromic in base 13.

It is not a de Polignac number, because 21408989 - 2⁴ = 21408973 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21408983) 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, 53189 + ... + 53589.

It is an arithmetic number, because the mean of its divisors is an integer number (1591920).

Almost surely, 2^21408989 is an apocalyptic number.

21408989 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21408989 is a deficient number, since it is larger than the sum of its proper divisors (4061731).

21408989 is a wasteful number, since it uses less digits than its factorization.

21408989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 700.

The product of its (nonzero) digits is 41472, while the sum is 41.

The square root of 21408989 is about 4626.9848713822. The cubic root of 21408989 is about 277.6719773729.

The spelling of 21408989 in words is "twenty-one million, four hundred eight thousand, nine hundred eighty-nine".