21211082172 has 648 divisors, whose sum is σ = 72766721664. Its totient is φ = 5374397952.

The previous prime is 21211082161. The next prime is 21211082173. The reversal of 21211082172 is 27128011212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211082173) 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 215 ways as a sum of consecutive naturals, for example, 316583283 + ... + 316583349.

Almost surely, 2^21211082172 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21211082172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36383360832).

21211082172 is an abundant number, since it is smaller than the sum of its proper divisors (51555639492).

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

21211082172 is a wasteful number, since it uses less digits than its factorization.

21211082172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157 (or 119 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

Adding to 21211082172 its reverse (27128011212), we get a palindrome (48339093384).

The spelling of 21211082172 in words is "twenty-one billion, two hundred eleven million, eighty-two thousand, one hundred seventy-two".