21655744 has 56 divisors (see below), whose sum is σ = 49377600. Its totient is φ = 9319680.

The previous prime is 21655729. The next prime is 21655759. The reversal of 21655744 is 44755612.

It is an interprime number because it is at equal distance from previous prime (21655729) and next prime (21655759).

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, 12567 + ... + 14185.

Almost surely, 2^21655744 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 21655744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24688800).

21655744 is an abundant number, since it is smaller than the sum of its proper divisors (27721856).

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

21655744 is a wasteful number, since it uses less digits than its factorization.

21655744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1661 (or 1651 counting only the distinct ones).

The product of its digits is 33600, while the sum is 34.

The square root of 21655744 is about 4653.5732507397. The cubic root of 21655744 is about 278.7346989664.

The spelling of 21655744 in words is "twenty-one million, six hundred fifty-five thousand, seven hundred forty-four".