21817793 has 2 divisors, whose sum is σ = 21817794. Its totient is φ = 21817792.

The previous prime is 21817759. The next prime is 21817799. The reversal of 21817793 is 39771812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20322064 + 1495729 = 4508^2 + 1223^2 .

It is a cyclic number.

It is not a de Polignac number, because 21817793 - 2¹² = 21813697 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 (21817799) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10908896 + 10908897.

It is an arithmetic number, because the mean of its divisors is an integer number (10908897).

Almost surely, 2^21817793 is an apocalyptic number.

It is an amenable number.

21817793 is a deficient number, since it is larger than the sum of its proper divisors (1).

21817793 is an equidigital number, since it uses as much as digits as its factorization.

21817793 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 21817793 is about 4670.9520442839. The cubic root of 21817793 is about 279.4282252072.

The spelling of 21817793 in words is "twenty-one million, eight hundred seventeen thousand, seven hundred ninety-three".