21147989 has 8 divisors (see below), whose sum is σ = 22187520. Its totient is φ = 20129200.

The previous prime is 21147967. The next prime is 21148013. The reversal of 21147989 is 98974112.

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

It is a cyclic number.

It is not a de Polignac number, because 21147989 - 2⁸ = 21147733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147289) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3077 + ... + 7194.

It is an arithmetic number, because the mean of its divisors is an integer number (2773440).

Almost surely, 2^21147989 is an apocalyptic number.

21147989 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21147989 is a deficient number, since it is larger than the sum of its proper divisors (1039531).

21147989 is a wasteful number, since it uses less digits than its factorization.

21147989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10371.

The product of its digits is 36288, while the sum is 41.

The square root of 21147989 is about 4598.6942712035. The cubic root of 21147989 is about 276.5389812573.

The spelling of 21147989 in words is "twenty-one million, one hundred forty-seven thousand, nine hundred eighty-nine".