21388534272 has 320 divisors, whose sum is σ = 73255311360. Its totient is φ = 6035116032.

The previous prime is 21388534243. The next prime is 21388534283. The reversal of 21388534272 is 27243588312.

21388534272 is a `hidden beast` number, since 2 + 13 + 88 + 534 + 27 + 2 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8030413 + ... + 8033075.

It is an arithmetic number, because the mean of its divisors is an integer number (228922848).

Almost surely, 2^21388534272 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 21388534272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36627655680).

21388534272 is an abundant number, since it is smaller than the sum of its proper divisors (51866777088).

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

21388534272 is an equidigital number, since it uses as much as digits as its factorization.

21388534272 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2780 (or 2758 counting only the distinct ones).

The product of its digits is 645120, while the sum is 45.

The spelling of 21388534272 in words is "twenty-one billion, three hundred eighty-eight million, five hundred thirty-four thousand, two hundred seventy-two".