21872036717 has 4 divisors (see below), whose sum is σ = 21873035676. Its totient is φ = 21871037760.

The previous prime is 21872036689. The next prime is 21872036741. The reversal of 21872036717 is 71763027812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13296165481 + 8575871236 = 115309^2 + 92606^2 .

It is a cyclic number.

It is not a de Polignac number, because 21872036717 - 2⁶ = 21872036653 is a prime.

It is a super-2 number, since 2×21872036717² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21872036117) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 465884 + ... + 510677.

It is an arithmetic number, because the mean of its divisors is an integer number (5468258919).

Almost surely, 2^21872036717 is an apocalyptic number.

It is an amenable number.

21872036717 is a deficient number, since it is larger than the sum of its proper divisors (998959).

21872036717 is an equidigital number, since it uses as much as digits as its factorization.

21872036717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 998958.

The product of its (nonzero) digits is 197568, while the sum is 44.

The spelling of 21872036717 in words is "twenty-one billion, eight hundred seventy-two million, thirty-six thousand, seven hundred seventeen".