21139009 has 2 divisors, whose sum is σ = 21139010. Its totient is φ = 21139008.

The previous prime is 21138989. The next prime is 21139031. The reversal of 21139009 is 90093112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18948609 + 2190400 = 4353^2 + 1480^2 .

It is a cyclic number.

It is not a de Polignac number, because 21139009 - 2⁵ = 21138977 is a prime.

It is a super-3 number, since 3×21139009³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21139709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569504 + 10569505.

It is an arithmetic number, because the mean of its divisors is an integer number (10569505).

Almost surely, 2^21139009 is an apocalyptic number.

It is an amenable number.

21139009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21139009 is an equidigital number, since it uses as much as digits as its factorization.

21139009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 21139009 is about 4597.7178034325. The cubic root of 21139009 is about 276.4998337741.

The spelling of 21139009 in words is "twenty-one million, one hundred thirty-nine thousand, nine".