21581472 has 96 divisors (see below), whose sum is σ = 62705664. Its totient is φ = 6444800.

The previous prime is 21581467. The next prime is 21581477. The reversal of 21581472 is 27418512.

It is an interprime number because it is at equal distance from previous prime (21581467) and next prime (21581477).

It is a tau number, because it is divible by the number of its divisors (96).

It is not an unprimeable number, because it can be changed into a prime (21581477) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 112897 + ... + 113087.

It is an arithmetic number, because the mean of its divisors is an integer number (653184).

Almost surely, 2^21581472 is an apocalyptic number.

21581472 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 21581472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31352832).

21581472 is an abundant number, since it is smaller than the sum of its proper divisors (41124192).

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

21581472 is a wasteful number, since it uses less digits than its factorization.

21581472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322 (or 314 counting only the distinct ones).

The product of its digits is 4480, while the sum is 30.

The square root of 21581472 is about 4645.5862923855. The cubic root of 21581472 is about 278.4156782028.

Adding to 21581472 its reverse (27418512), we get a palindrome (48999984).

The spelling of 21581472 in words is "twenty-one million, five hundred eighty-one thousand, four hundred seventy-two".