21086839 has 2 divisors, whose sum is σ = 21086840. Its totient is φ = 21086838.

The previous prime is 21086753. The next prime is 21086861. The reversal of 21086839 is 93868012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21086839 - 2⁹ = 21086327 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21086798 and 21086807.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21084839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10543419 + 10543420.

It is an arithmetic number, because the mean of its divisors is an integer number (10543420).

Almost surely, 2^21086839 is an apocalyptic number.

21086839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21086839 is an equidigital number, since it uses as much as digits as its factorization.

21086839 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21086839 is about 4592.0408317000. The cubic root of 21086839 is about 276.2721838822.

The spelling of 21086839 in words is "twenty-one million, eighty-six thousand, eight hundred thirty-nine".