21090456 has 96 divisors (see below), whose sum is σ = 62462400. Its totient is φ = 6648480.

The previous prime is 21090439. The next prime is 21090457. The reversal of 21090456 is 65409012.

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 (21090457) 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, 36651 + ... + 37221.

It is an arithmetic number, because the mean of its divisors is an integer number (650650).

Almost surely, 2^21090456 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 21090456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31231200).

21090456 is an abundant number, since it is smaller than the sum of its proper divisors (41371944).

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

21090456 is a wasteful number, since it uses less digits than its factorization.

21090456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 611 (or 595 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21090456 is about 4592.4346484191. The cubic root of 21090456 is about 276.2879791903.

Adding to 21090456 its reverse (65409012), we get a palindrome (86499468).

The spelling of 21090456 in words is "twenty-one million, ninety thousand, four hundred fifty-six".