21405589 has 2 divisors, whose sum is σ = 21405590. Its totient is φ = 21405588.

The previous prime is 21405569. The next prime is 21405607. The reversal of 21405589 is 98550412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12602500 + 8803089 = 3550^2 + 2967^2 .

It is a cyclic number.

It is not a de Polignac number, because 21405589 - 2²¹ = 19308437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405569) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702794 + 10702795.

It is an arithmetic number, because the mean of its divisors is an integer number (10702795).

Almost surely, 2^21405589 is an apocalyptic number.

It is an amenable number.

21405589 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405589 is an equidigital number, since it uses as much as digits as its factorization.

21405589 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 21405589 is about 4626.6174469044. The cubic root of 21405589 is about 277.6572773995.

The spelling of 21405589 in words is "twenty-one million, four hundred five thousand, five hundred eighty-nine".