21791744 has 44 divisors (see below), whose sum is σ = 46941804. Its totient is φ = 10051584.

The previous prime is 21791743. The next prime is 21791747. The reversal of 21791744 is 44719712.

It can be written as a sum of positive squares in 2 ways, for example, as 1721344 + 20070400 = 1312^2 + 4480^2 .

It is not an unprimeable number, because it can be changed into a prime (21791743) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12494 + ... + 14130.

Almost surely, 2^21791744 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 21791744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23470902).

21791744 is an abundant number, since it is smaller than the sum of its proper divisors (25150060).

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

21791744 is a wasteful number, since it uses less digits than its factorization.

21791744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1670 (or 1652 counting only the distinct ones).

The product of its digits is 14112, while the sum is 35.

The square root of 21791744 is about 4668.1628077864. The cubic root of 21791744 is about 279.3169746548.

The spelling of 21791744 in words is "twenty-one million, seven hundred ninety-one thousand, seven hundred forty-four".