21917609917 has 4 divisors (see below), whose sum is σ = 25048697056. Its totient is φ = 18786522780.

The previous prime is 21917609893. The next prime is 21917609957. The reversal of 21917609917 is 71990671912.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21917609917 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917609957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1565543559 + ... + 1565543572.

It is an arithmetic number, because the mean of its divisors is an integer number (6262174264).

Almost surely, 2^21917609917 is an apocalyptic number.

It is an amenable number.

21917609917 is a deficient number, since it is larger than the sum of its proper divisors (3131087139).

21917609917 is an equidigital number, since it uses as much as digits as its factorization.

21917609917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3131087138.

The product of its (nonzero) digits is 428652, while the sum is 52.

The spelling of 21917609917 in words is "twenty-one billion, nine hundred seventeen million, six hundred nine thousand, nine hundred seventeen".