21090472 has 64 divisors (see below), whose sum is σ = 45964800. Its totient is φ = 8985600.

The previous prime is 21090467. The next prime is 21090473. The reversal of 21090472 is 27409012.

It is not an unprimeable number, because it can be changed into a prime (21090473) 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, 139597 + ... + 139747.

It is an arithmetic number, because the mean of its divisors is an integer number (718200).

Almost surely, 2^21090472 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 21090472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22982400).

21090472 is an abundant number, since it is smaller than the sum of its proper divisors (24874328).

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

21090472 is a wasteful number, since it uses less digits than its factorization.

21090472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266 (or 262 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21090472 is about 4592.4363904141. The cubic root of 21090472 is about 276.2880490577.

Adding to 21090472 its reverse (27409012), we get a palindrome (48499484).

The spelling of 21090472 in words is "twenty-one million, ninety thousand, four hundred seventy-two".