21718944 has 72 divisors (see below), whose sum is σ = 66525732. Its totient is φ = 6681600.

The previous prime is 21718943. The next prime is 21718973. The reversal of 21718944 is 44981712.

It can be written as a sum of positive squares in 2 ways, for example, as 21344400 + 374544 = 4620^2 + 612^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a junction number, because it is equal to n+sod(n) for n = 21718899 and 21718908.

It is not an unprimeable number, because it can be changed into a prime (21718943) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 844 + ... + 6644.

Almost surely, 2^21718944 is an apocalyptic number.

21718944 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21718944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33262866).

21718944 is an abundant number, since it is smaller than the sum of its proper divisors (44806788).

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

21718944 is a wasteful number, since it uses less digits than its factorization.

21718944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5830 (or 5819 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 21718944 is about 4660.3587844714. The cubic root of 21718944 is about 279.0055882027.

The spelling of 21718944 in words is "twenty-one million, seven hundred eighteen thousand, nine hundred forty-four".