21517723238399 has 8 divisors (see below), whose sum is σ = 21923973233712. Its totient is φ = 21111482695680.

The previous prime is 21517723238387. The next prime is 21517723238441. The reversal of 21517723238399 is 99383232771512.

It is a Cunningham number, because it is equal to 4638720²-1.

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

It is a cyclic number.

It is not a de Polignac number, because 21517723238399 - 2¹⁶ = 21517723172863 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 (21517723238309) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2319359 + ... + 6958079.

It is an arithmetic number, because the mean of its divisors is an integer number (2740496654214).

Almost surely, 2^{21517723238399} is an apocalyptic number.

21517723238399 is a deficient number, since it is larger than the sum of its proper divisors (406249995313).

21517723238399 is an equidigital number, since it uses as much as digits as its factorization.

21517723238399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4726297.

The product of its digits is 34292160, while the sum is 62.

The spelling of 21517723238399 in words is "twenty-one trillion, five hundred seventeen billion, seven hundred twenty-three million, two hundred thirty-eight thousand, three hundred ninety-nine".