21209472 has 192 divisors, whose sum is σ = 69951600. Its totient is φ = 6303744.

The previous prime is 21209471. The next prime is 21209537. The reversal of 21209472 is 27490212.

It is a tau number, because it is divible by the number of its divisors (192).

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 (21209471) 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, 1116279 + ... + 1116297.

Almost surely, 2^21209472 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 21209472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34975800).

21209472 is an abundant number, since it is smaller than the sum of its proper divisors (48742128).

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

21209472 is a wasteful number, since it uses less digits than its factorization.

21209472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78 (or 41 counting only the distinct ones).

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

The square root of 21209472 is about 4605.3742518931. The cubic root of 21209472 is about 276.8067135040.

Adding to 21209472 its reverse (27490212), we get a palindrome (48699684).

The spelling of 21209472 in words is "twenty-one million, two hundred nine thousand, four hundred seventy-two".