21791159217 has 10 divisors (see below), whose sum is σ = 32552225618. Its totient is φ = 14527439424.

The previous prime is 21791159209. The next prime is 21791159227. The reversal of 21791159217 is 71295119712.

It can be written as a sum of positive squares in only one way, i.e., 21788416881 + 2742336 = 147609^2 + 1656^2 .

It is not a de Polignac number, because 21791159217 - 2³ = 21791159209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21791159227) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 134513248 + ... + 134513409.

Almost surely, 2^21791159217 is an apocalyptic number.

21791159217 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21791159217 is a deficient number, since it is larger than the sum of its proper divisors (10761066401).

21791159217 is an equidigital number, since it uses as much as digits as its factorization.

21791159217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269026669 (or 269026660 counting only the distinct ones).

The product of its digits is 79380, while the sum is 45.

The spelling of 21791159217 in words is "twenty-one billion, seven hundred ninety-one million, one hundred fifty-nine thousand, two hundred seventeen".