21381372 has 36 divisors (see below), whose sum is σ = 54281136. Its totient is φ = 7096320.

The previous prime is 21381361. The next prime is 21381379. The reversal of 21381372 is 27318312.

21381372 is a `hidden beast` number, since 213 + 81 + 372 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381379) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8097 + ... + 10407.

Almost surely, 2^21381372 is an apocalyptic number.

It is an amenable number.

21381372 is an abundant number, since it is smaller than the sum of its proper divisors (32899764).

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

21381372 is a wasteful number, since it uses less digits than its factorization.

21381372 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2578 (or 2573 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21381372 is about 4623.9995674740. Note that the first 3 decimals coincide. The cubic root of 21381372 is about 277.5525296223.

Adding to 21381372 its reverse (27318312), we get a palindrome (48699684).

The spelling of 21381372 in words is "twenty-one million, three hundred eighty-one thousand, three hundred seventy-two".