21178793 has 2 divisors, whose sum is σ = 21178794. Its totient is φ = 21178792.

The previous prime is 21178783. The next prime is 21178813. The reversal of 21178793 is 39787112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13271449 + 7907344 = 3643^2 + 2812^2 .

It is a cyclic number.

It is not a de Polignac number, because 21178793 - 2⁴ = 21178777 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21178733) 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, 10589396 + 10589397.

It is an arithmetic number, because the mean of its divisors is an integer number (10589397).

Almost surely, 2^21178793 is an apocalyptic number.

It is an amenable number.

21178793 is a deficient number, since it is larger than the sum of its proper divisors (1).

21178793 is an equidigital number, since it uses as much as digits as its factorization.

21178793 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21178793 is about 4602.0422640389. The cubic root of 21178793 is about 276.6731843112.

The spelling of 21178793 in words is "twenty-one million, one hundred seventy-eight thousand, seven hundred ninety-three".