21745424 has 40 divisors (see below), whose sum is σ = 44684640. Its totient is φ = 10222848.

The previous prime is 21745421. The next prime is 21745429. The reversal of 21745424 is 42454712.

21745424 = 182² + 183² + ... + 414².

It is not an unprimeable number, because it can be changed into a prime (21745421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 70679 + ... + 70985.

It is an arithmetic number, because the mean of its divisors is an integer number (1117116).

Almost surely, 2^21745424 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 21745424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22342320).

21745424 is an abundant number, since it is smaller than the sum of its proper divisors (22939216).

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

21745424 is a wasteful number, since it uses less digits than its factorization.

21745424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 567 (or 561 counting only the distinct ones).

The product of its digits is 8960, while the sum is 29.

The square root of 21745424 is about 4663.1989020414. The cubic root of 21745424 is about 279.1189311514.

The spelling of 21745424 in words is "twenty-one million, seven hundred forty-five thousand, four hundred twenty-four".