21085837 has 2 divisors, whose sum is σ = 21085838. Its totient is φ = 21085836.

The previous prime is 21085789. The next prime is 21085847. The reversal of 21085837 is 73858012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20738916 + 346921 = 4554^2 + 589^2 .

It is a cyclic number.

It is not a de Polignac number, because 21085837 - 2⁷ = 21085709 is a prime.

It is a super-2 number, since 2×21085837² = 889225043981138, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21085847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542918 + 10542919.

It is an arithmetic number, because the mean of its divisors is an integer number (10542919).

Almost surely, 2^21085837 is an apocalyptic number.

It is an amenable number.

21085837 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085837 is an equidigital number, since it uses as much as digits as its factorization.

21085837 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 21085837 is about 4591.9317285866. The cubic root of 21085837 is about 276.2678078649.

The spelling of 21085837 in words is "twenty-one million, eighty-five thousand, eight hundred thirty-seven".