21191873 has 2 divisors, whose sum is σ = 21191874. Its totient is φ = 21191872.

The previous prime is 21191857. The next prime is 21191917. The reversal of 21191873 is 37819112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21049744 + 142129 = 4588^2 + 377^2 .

It is a cyclic number.

It is not a de Polignac number, because 21191873 - 2⁴ = 21191857 is a prime.

It is not a weakly prime, because it can be changed into another prime (21191803) 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, 10595936 + 10595937.

It is an arithmetic number, because the mean of its divisors is an integer number (10595937).

Almost surely, 2^21191873 is an apocalyptic number.

It is an amenable number.

21191873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21191873 is an equidigital number, since it uses as much as digits as its factorization.

21191873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 32.

The square root of 21191873 is about 4603.4631528883. The cubic root of 21191873 is about 276.7301302776.

The spelling of 21191873 in words is "twenty-one million, one hundred ninety-one thousand, eight hundred seventy-three".