21843975217 has 2 divisors, whose sum is σ = 21843975218. Its totient is φ = 21843975216.

The previous prime is 21843975143. The next prime is 21843975221. The reversal of 21843975217 is 71257934812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18292292001 + 3551683216 = 135249^2 + 59596^2 .

It is a cyclic number.

It is not a de Polignac number, because 21843975217 - 2²³ = 21835586609 is a prime.

It is not a weakly prime, because it can be changed into another prime (21843975277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10921987608 + 10921987609.

It is an arithmetic number, because the mean of its divisors is an integer number (10921987609).

Almost surely, 2^21843975217 is an apocalyptic number.

It is an amenable number.

21843975217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21843975217 is an equidigital number, since it uses as much as digits as its factorization.

21843975217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 846720, while the sum is 49.

The spelling of 21843975217 in words is "twenty-one billion, eight hundred forty-three million, nine hundred seventy-five thousand, two hundred seventeen".