21026839 has 2 divisors, whose sum is σ = 21026840. Its totient is φ = 21026838.

The previous prime is 21026821. The next prime is 21026851. The reversal of 21026839 is 93862012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21026839 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21026839.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21026869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513419 + 10513420.

It is an arithmetic number, because the mean of its divisors is an integer number (10513420).

Almost surely, 2^21026839 is an apocalyptic number.

21026839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026839 is an equidigital number, since it uses as much as digits as its factorization.

21026839 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21026839 is about 4585.5031348806. The cubic root of 21026839 is about 276.0099021512.

The spelling of 21026839 in words is "twenty-one million, twenty-six thousand, eight hundred thirty-nine".