21659789 has 2 divisors, whose sum is σ = 21659790. Its totient is φ = 21659788.

The previous prime is 21659779. The next prime is 21659797. The reversal of 21659789 is 98795612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20097289 + 1562500 = 4483^2 + 1250^2 .

It is a cyclic number.

It is not a de Polignac number, because 21659789 - 2¹⁶ = 21594253 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21659719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10829894 + 10829895.

It is an arithmetic number, because the mean of its divisors is an integer number (10829895).

Almost surely, 2^21659789 is an apocalyptic number.

It is an amenable number.

21659789 is a deficient number, since it is larger than the sum of its proper divisors (1).

21659789 is an equidigital number, since it uses as much as digits as its factorization.

21659789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 272160, while the sum is 47.

The square root of 21659789 is about 4654.0078427093. The cubic root of 21659789 is about 278.7520525096.

The spelling of 21659789 in words is "twenty-one million, six hundred fifty-nine thousand, seven hundred eighty-nine".