21308789 has 2 divisors, whose sum is σ = 21308790. Its totient is φ = 21308788.

The previous prime is 21308767. The next prime is 21308801. The reversal of 21308789 is 98780312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13140625 + 8168164 = 3625^2 + 2858^2 .

It is a cyclic number.

It is not a de Polignac number, because 21308789 - 2¹⁶ = 21243253 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 (21308759) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10654394 + 10654395.

It is an arithmetic number, because the mean of its divisors is an integer number (10654395).

Almost surely, 2^21308789 is an apocalyptic number.

It is an amenable number.

21308789 is a deficient number, since it is larger than the sum of its proper divisors (1).

21308789 is an equidigital number, since it uses as much as digits as its factorization.

21308789 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 21308789 is about 4616.1443868233. The cubic root of 21308789 is about 277.2381058594.

The spelling of 21308789 in words is "twenty-one million, three hundred eight thousand, seven hundred eighty-nine".