21491456 has 72 divisors (see below), whose sum is σ = 50037120. Its totient is φ = 9022464.

The previous prime is 21491441. The next prime is 21491461. The reversal of 21491456 is 65419412.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 119975 + ... + 120153.

It is an arithmetic number, because the mean of its divisors is an integer number (694960).

Almost surely, 2^21491456 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 21491456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25018560).

21491456 is an abundant number, since it is smaller than the sum of its proper divisors (28545664).

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

21491456 is an equidigital number, since it uses as much as digits as its factorization.

21491456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269 (or 255 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 21491456 is about 4635.8878329830. The cubic root of 21491456 is about 278.0280495480.

The spelling of 21491456 in words is "twenty-one million, four hundred ninety-one thousand, four hundred fifty-six".