21791873 has 2 divisors, whose sum is σ = 21791874. Its totient is φ = 21791872.

The previous prime is 21791843. The next prime is 21791881. The reversal of 21791873 is 37819712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21464689 + 327184 = 4633^2 + 572^2 .

It is a cyclic number.

It is not a de Polignac number, because 21791873 - 2⁸ = 21791617 is a prime.

It is not a weakly prime, because it can be changed into another prime (21791843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10895936 + 10895937.

It is an arithmetic number, because the mean of its divisors is an integer number (10895937).

Almost surely, 2^21791873 is an apocalyptic number.

It is an amenable number.

21791873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21791873 is an equidigital number, since it uses as much as digits as its factorization.

21791873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21168, while the sum is 38.

The square root of 21791873 is about 4668.1766247647. The cubic root of 21791873 is about 279.3175258088.

The spelling of 21791873 in words is "twenty-one million, seven hundred ninety-one thousand, eight hundred seventy-three".