21517272 has 192 divisors, whose sum is σ = 73872000. Its totient is φ = 5769792.

The previous prime is 21517271. The next prime is 21517283. The reversal of 21517272 is 27271512.

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 (21517271) 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 47 ways as a sum of consecutive naturals, for example, 201043 + ... + 201149.

It is an arithmetic number, because the mean of its divisors is an integer number (384750).

Almost surely, 2^21517272 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 21517272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36936000).

21517272 is an abundant number, since it is smaller than the sum of its proper divisors (52354728).

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

21517272 is a wasteful number, since it uses less digits than its factorization.

21517272 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155 (or 138 counting only the distinct ones).

The product of its digits is 1960, while the sum is 27.

The square root of 21517272 is about 4638.6713615000. The cubic root of 21517272 is about 278.1393294305.

Adding to 21517272 its reverse (27271512), we get a palindrome (48788784).

The spelling of 21517272 in words is "twenty-one million, five hundred seventeen thousand, two hundred seventy-two".