21891456 has 96 divisors (see below), whose sum is σ = 65133120. Its totient is φ = 7050240.

The previous prime is 21891449. The next prime is 21891473. The reversal of 21891456 is 65419812.

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

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21891456.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35406 + ... + 36018.

It is an arithmetic number, because the mean of its divisors is an integer number (678470).

Almost surely, 2^21891456 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 21891456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32566560).

21891456 is an abundant number, since it is smaller than the sum of its proper divisors (43241664).

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

21891456 is a wasteful number, since it uses less digits than its factorization.

21891456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664 (or 649 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 21891456 is about 4678.8306231365. The cubic root of 21891456 is about 279.7423480191.

The spelling of 21891456 in words is "twenty-one million, eight hundred ninety-one thousand, four hundred fifty-six".