21187438272 has 672 divisors, whose sum is σ = 84621648384. Its totient is φ = 5076172800.

The previous prime is 21187438271. The next prime is 21187438297. The reversal of 21187438272 is 27283478112.

21187438272 is a `hidden beast` number, since 21 + 187 + 4 + 382 + 72 = 666.

It is a tau number, because it is divible by the number of its divisors (672).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21187438271) 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 95 ways as a sum of consecutive naturals, for example, 15566872 + ... + 15568232.

It is an arithmetic number, because the mean of its divisors is an integer number (125925072).

Almost surely, 2^21187438272 is an apocalyptic number.

21187438272 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21187438272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42310824192).

21187438272 is an abundant number, since it is smaller than the sum of its proper divisors (63434210112).

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

21187438272 is a wasteful number, since it uses less digits than its factorization.

21187438272 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1419 (or 1397 counting only the distinct ones).

The product of its digits is 301056, while the sum is 45.

The spelling of 21187438272 in words is "twenty-one billion, one hundred eighty-seven million, four hundred thirty-eight thousand, two hundred seventy-two".