21857873 has 2 divisors, whose sum is σ = 21857874. Its totient is φ = 21857872.

The previous prime is 21857863. The next prime is 21857887. The reversal of 21857873 is 37875812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17581249 + 4276624 = 4193^2 + 2068^2 .

It is a cyclic number.

It is not a de Polignac number, because 21857873 - 2⁸ = 21857617 is a prime.

It is a super-2 number, since 2×21857873² = 955533224168258, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21857873.

It is not a weakly prime, because it can be changed into another prime (21857813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10928936 + 10928937.

It is an arithmetic number, because the mean of its divisors is an integer number (10928937).

Almost surely, 2^21857873 is an apocalyptic number.

It is an amenable number.

21857873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21857873 is an equidigital number, since it uses as much as digits as its factorization.

21857873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 94080, while the sum is 41.

The square root of 21857873 is about 4675.2404216254. The cubic root of 21857873 is about 279.5992268039.

The spelling of 21857873 in words is "twenty-one million, eight hundred fifty-seven thousand, eight hundred seventy-three".