21789689 has 2 divisors, whose sum is σ = 21789690. Its totient is φ = 21789688.

The previous prime is 21789679. The next prime is 21789709. The reversal of 21789689 is 98698712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16949689 + 4840000 = 4117^2 + 2200^2 .

It is a cyclic number.

It is not a de Polignac number, because 21789689 - 2²⁴ = 5012473 is a prime.

It is not a weakly prime, because it can be changed into another prime (21789619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10894844 + 10894845.

It is an arithmetic number, because the mean of its divisors is an integer number (10894845).

Almost surely, 2^21789689 is an apocalyptic number.

It is an amenable number.

21789689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21789689 is an equidigital number, since it uses as much as digits as its factorization.

21789689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 435456, while the sum is 50.

The square root of 21789689 is about 4667.9426945926. The cubic root of 21789689 is about 279.3081943505.

The spelling of 21789689 in words is "twenty-one million, seven hundred eighty-nine thousand, six hundred eighty-nine".