21388617817 has 8 divisors (see below), whose sum is σ = 24585431616. Its totient is φ = 18227128272.

The previous prime is 21388617707. The next prime is 21388617821. The reversal of 21388617817 is 71871688312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21388617817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21388611817) 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 7 ways as a sum of consecutive naturals, for example, 8829763 + ... + 8832184.

It is an arithmetic number, because the mean of its divisors is an integer number (3073178952).

Almost surely, 2^21388617817 is an apocalyptic number.

It is an amenable number.

21388617817 is a deficient number, since it is larger than the sum of its proper divisors (3196813799).

21388617817 is a wasteful number, since it uses less digits than its factorization.

21388617817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17662127.

The product of its digits is 903168, while the sum is 52.

The spelling of 21388617817 in words is "twenty-one billion, three hundred eighty-eight million, six hundred seventeen thousand, eight hundred seventeen".