21026389 has 2 divisors, whose sum is σ = 21026390. Its totient is φ = 21026388.

The previous prime is 21026381. The next prime is 21026419. The reversal of 21026389 is 98362012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21003889 + 22500 = 4583^2 + 150^2 .

It is a cyclic number.

It is not a de Polignac number, because 21026389 - 2³ = 21026381 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21026389.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21026381) 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 as a sum of consecutive naturals, namely, 10513194 + 10513195.

It is an arithmetic number, because the mean of its divisors is an integer number (10513195).

Almost surely, 2^21026389 is an apocalyptic number.

It is an amenable number.

21026389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026389 is an equidigital number, since it uses as much as digits as its factorization.

21026389 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21026389 is about 4585.4540669382. The cubic root of 21026389 is about 276.0079331543.

The spelling of 21026389 in words is "twenty-one million, twenty-six thousand, three hundred eighty-nine".