21217221712 has 20 divisors (see below), whose sum is σ = 41472161460. Its totient is φ = 10514728448.

The previous prime is 21217221709. The next prime is 21217221719. The reversal of 21217221712 is 21712271212.

It can be written as a sum of positive squares in 2 ways, for example, as 3920763456 + 17296458256 = 62616^2 + 131516^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21217221719) 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, 5865787 + ... + 5869402.

It is an arithmetic number, because the mean of its divisors is an integer number (2073608073).

Almost surely, 2^21217221712 is an apocalyptic number.

It is an amenable number.

21217221712 is a deficient number, since it is larger than the sum of its proper divisors (20254939748).

21217221712 is a wasteful number, since it uses less digits than its factorization.

21217221712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11735310 (or 11735304 counting only the distinct ones).

The product of its digits is 1568, while the sum is 28.

Adding to 21217221712 its reverse (21712271212), we get a palindrome (42929492924).

The spelling of 21217221712 in words is "twenty-one billion, two hundred seventeen million, two hundred twenty-one thousand, seven hundred twelve".