21712221220 has 24 divisors (see below), whose sum is σ = 45666823608. Its totient is φ = 8671334400.

The previous prime is 21712221217. The next prime is 21712221221. The reversal of 21712221220 is 2212221712.

It can be written as a sum of positive squares in 4 ways, for example, as 2846649316 + 18865571904 = 53354^2 + 137352^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21712221191 and 21712221200.

It is not an unprimeable number, because it can be changed into a prime (21712221221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 833991 + ... + 859630.

It is an arithmetic number, because the mean of its divisors is an integer number (1902784317).

Almost surely, 2^21712221220 is an apocalyptic number.

21712221220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21712221220 is an abundant number, since it is smaller than the sum of its proper divisors (23954602388).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21712221220 is a wasteful number, since it uses less digits than its factorization.

21712221220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1694271 (or 1694269 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 22.

Adding to 21712221220 its reverse (2212221712), we get a palindrome (23924442932).

The spelling of 21712221220 in words is "twenty-one billion, seven hundred twelve million, two hundred twenty-one thousand, two hundred twenty".