21271215456 has 144 divisors (see below), whose sum is σ = 64207306800. Its totient is φ = 6656753664.

The previous prime is 21271215451. The next prime is 21271215463. The reversal of 21271215456 is 65451217212.

21271215456 is a `hidden beast` number, since 21 + 2 + 71 + 21 + 545 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21271215456.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21271215451) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2046240 + ... + 2056608.

It is an arithmetic number, because the mean of its divisors is an integer number (445884075).

Almost surely, 2^21271215456 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 21271215456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32103653400).

21271215456 is an abundant number, since it is smaller than the sum of its proper divisors (42936091344).

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

21271215456 is a wasteful number, since it uses less digits than its factorization.

21271215456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10821 (or 10810 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The spelling of 21271215456 in words is "twenty-one billion, two hundred seventy-one million, two hundred fifteen thousand, four hundred fifty-six".