21639329 has 2 divisors, whose sum is σ = 21639330. Its totient is φ = 21639328.

The previous prime is 21639313. The next prime is 21639337. The reversal of 21639329 is 92393612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15523600 + 6115729 = 3940^2 + 2473^2 .

It is a cyclic number.

It is not a de Polignac number, because 21639329 - 2⁴ = 21639313 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21633329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10819664 + 10819665.

It is an arithmetic number, because the mean of its divisors is an integer number (10819665).

Almost surely, 2^21639329 is an apocalyptic number.

It is an amenable number.

21639329 is a deficient number, since it is larger than the sum of its proper divisors (1).

21639329 is an equidigital number, since it uses as much as digits as its factorization.

21639329 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 35.

The square root of 21639329 is about 4651.8092179280. The cubic root of 21639329 is about 278.6642544287.

The spelling of 21639329 in words is "twenty-one million, six hundred thirty-nine thousand, three hundred twenty-nine".