21081589 has 2 divisors, whose sum is σ = 21081590. Its totient is φ = 21081588.

The previous prime is 21081569. The next prime is 21081611. The reversal of 21081589 is 98518012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13380964 + 7700625 = 3658^2 + 2775^2 .

It is a cyclic number.

It is not a de Polignac number, because 21081589 - 2²¹ = 18984437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21081509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10540794 + 10540795.

It is an arithmetic number, because the mean of its divisors is an integer number (10540795).

Almost surely, 2^21081589 is an apocalyptic number.

It is an amenable number.

21081589 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081589 is an equidigital number, since it uses as much as digits as its factorization.

21081589 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 21081589 is about 4591.4691548566. The cubic root of 21081589 is about 276.2492541083.

The spelling of 21081589 in words is "twenty-one million, eighty-one thousand, five hundred eighty-nine".