21217163691 has 8 divisors (see below), whose sum is σ = 28353994240. Its totient is φ = 14112554472.

The previous prime is 21217163689. The next prime is 21217163729. The reversal of 21217163691 is 19636171212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21217163691 - 2¹ = 21217163689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21217163641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8053795 + ... + 8056428.

It is an arithmetic number, because the mean of its divisors is an integer number (3544249280).

Almost surely, 2^21217163691 is an apocalyptic number.

21217163691 is a deficient number, since it is larger than the sum of its proper divisors (7136830549).

21217163691 is a wasteful number, since it uses less digits than its factorization.

21217163691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16110665.

The product of its digits is 27216, while the sum is 39.

The spelling of 21217163691 in words is "twenty-one billion, two hundred seventeen million, one hundred sixty-three thousand, six hundred ninety-one".