21409272 has 56 divisors (see below), whose sum is σ = 60202440. Its totient is φ = 7134480.

The previous prime is 21409249. The next prime is 21409277. The reversal of 21409272 is 27290412.

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 (21409277) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 3997 + ... + 7667.

Almost surely, 2^21409272 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 21409272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30101220).

21409272 is an abundant number, since it is smaller than the sum of its proper divisors (38793168).

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

21409272 is an equidigital number, since it uses as much as digits as its factorization.

21409272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3695 (or 3676 counting only the distinct ones).

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

The square root of 21409272 is about 4627.0154527514. The cubic root of 21409272 is about 277.6732008593.

Adding to 21409272 its reverse (27290412), we get a palindrome (48699684).

The spelling of 21409272 in words is "twenty-one million, four hundred nine thousand, two hundred seventy-two".