21971882217 has 4 divisors (see below), whose sum is σ = 29295842960. Its totient is φ = 14647921476.

The previous prime is 21971882201. The next prime is 21971882227. The reversal of 21971882217 is 71228817912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21971882217 - 2⁴ = 21971882201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21971882227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3661980367 + ... + 3661980372.

It is an arithmetic number, because the mean of its divisors is an integer number (7323960740).

Almost surely, 2^21971882217 is an apocalyptic number.

It is an amenable number.

21971882217 is a deficient number, since it is larger than the sum of its proper divisors (7323960743).

21971882217 is an equidigital number, since it uses as much as digits as its factorization.

21971882217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7323960742.

The product of its digits is 225792, while the sum is 48.

The spelling of 21971882217 in words is "twenty-one billion, nine hundred seventy-one million, eight hundred eighty-two thousand, two hundred seventeen".