21241720 has 16 divisors (see below), whose sum is σ = 47793960. Its totient is φ = 8496672.

The previous prime is 21241667. The next prime is 21241723. The reversal of 21241720 is 2714212.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21241723) 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, 265482 + ... + 265561.

Almost surely, 2^21241720 is an apocalyptic number.

21241720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21241720 is an abundant number, since it is smaller than the sum of its proper divisors (26552240).

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

21241720 is a wasteful number, since it uses less digits than its factorization.

21241720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 531054 (or 531050 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 21241720 is about 4608.8740490493. The cubic root of 21241720 is about 276.9469329717.

Adding to 21241720 its reverse (2714212), we get a palindrome (23955932).

It can be divided in two parts, 2124 and 1720, that added together give a square (3844 = 62²).

The spelling of 21241720 in words is "twenty-one million, two hundred forty-one thousand, seven hundred twenty".