21839009 has 2 divisors, whose sum is σ = 21839010. Its totient is φ = 21839008.

The previous prime is 21839003. The next prime is 21839011. The reversal of 21839009 is 90093812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12229009 + 9610000 = 3497^2 + 3100^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21839009 is a prime.

Together with 21839011, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21839003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10919504 + 10919505.

It is an arithmetic number, because the mean of its divisors is an integer number (10919505).

Almost surely, 2^21839009 is an apocalyptic number.

It is an amenable number.

21839009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21839009 is an equidigital number, since it uses as much as digits as its factorization.

21839009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 21839009 is about 4673.2225498044. Note that the first 3 decimals coincide. The cubic root of 21839009 is about 279.5187694808.

The spelling of 21839009 in words is "twenty-one million, eight hundred thirty-nine thousand, nine".