21085879 has 2 divisors, whose sum is σ = 21085880. Its totient is φ = 21085878.

The previous prime is 21085853. The next prime is 21085907. The reversal of 21085879 is 97858012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21085879 - 2⁵ = 21085847 is a prime.

It is a super-2 number, since 2×21085879² = 889228586405282, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21085279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542939 + 10542940.

It is an arithmetic number, because the mean of its divisors is an integer number (10542940).

Almost surely, 2^21085879 is an apocalyptic number.

21085879 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085879 is an equidigital number, since it uses as much as digits as its factorization.

21085879 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 21085879 is about 4591.9363018230. The cubic root of 21085879 is about 276.2679912936.

The spelling of 21085879 in words is "twenty-one million, eighty-five thousand, eight hundred seventy-nine".