21789989 has 8 divisors (see below), whose sum is σ = 23788632. Its totient is φ = 19837440.

The previous prime is 21789967. The next prime is 21789997. The reversal of 21789989 is 98998712.

It can be written as a sum of positive squares in 4 ways, for example, as 2280100 + 19509889 = 1510^2 + 4417^2 .

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-21789989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21789989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21789919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10532 + ... + 12429.

It is an arithmetic number, because the mean of its divisors is an integer number (2973579).

Almost surely, 2^21789989 is an apocalyptic number.

It is an amenable number.

21789989 is a deficient number, since it is larger than the sum of its proper divisors (1998643).

21789989 is a wasteful number, since it uses less digits than its factorization.

21789989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23047.

The product of its digits is 653184, while the sum is 53.

The square root of 21789989 is about 4667.9748285525. The cubic root of 21789989 is about 279.3094761812.

It can be divided in two parts, 2178 and 9989, that added together give a cube (12167 = 23³).

The spelling of 21789989 in words is "twenty-one million, seven hundred eighty-nine thousand, nine hundred eighty-nine".