21668839 has 2 divisors, whose sum is σ = 21668840. Its totient is φ = 21668838.

The previous prime is 21668827. The next prime is 21668851. The reversal of 21668839 is 93886612.

It is a balanced prime because it is at equal distance from previous prime (21668827) and next prime (21668851).

It is a cyclic number.

It is not a de Polignac number, because 21668839 - 2⁵ = 21668807 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21668795 and 21668804.

It is a congruent number.

It is a weakly prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10834419 + 10834420.

It is an arithmetic number, because the mean of its divisors is an integer number (10834420).

Almost surely, 2^21668839 is an apocalyptic number.

21668839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21668839 is an equidigital number, since it uses as much as digits as its factorization.

21668839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 43.

The square root of 21668839 is about 4654.9800214394. The cubic root of 21668839 is about 278.7908702901.

The spelling of 21668839 in words is "twenty-one million, six hundred sixty-eight thousand, eight hundred thirty-nine".