21908839 has 2 divisors, whose sum is σ = 21908840. Its totient is φ = 21908838.

The previous prime is 21908837. The next prime is 21908849. The reversal of 21908839 is 93880912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21908839 - 2¹ = 21908837 is a prime.

Together with 21908837, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21908837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10954419 + 10954420.

It is an arithmetic number, because the mean of its divisors is an integer number (10954420).

Almost surely, 2^21908839 is an apocalyptic number.

21908839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21908839 is an equidigital number, since it uses as much as digits as its factorization.

21908839 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 21908839 is about 4680.6878767976. The cubic root of 21908839 is about 279.8163719473.

The spelling of 21908839 in words is "twenty-one million, nine hundred eight thousand, eight hundred thirty-nine".