21724620 has 48 divisors (see below), whose sum is σ = 61329408. Its totient is φ = 5745600.

The previous prime is 21724613. The next prime is 21724621. The reversal of 21724620 is 2642712.

It is a super-2 number, since 2×21724620² = 943918228288800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21724621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6195 + ... + 9045.

It is an arithmetic number, because the mean of its divisors is an integer number (1277696).

Almost surely, 2^21724620 is an apocalyptic number.

21724620 is a gapful number since it is divisible by the number (20) 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 21724620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30664704).

21724620 is an abundant number, since it is smaller than the sum of its proper divisors (39604788).

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

21724620 is a wasteful number, since it uses less digits than its factorization.

21724620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2990 (or 2988 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 21724620 is about 4660.9677106798. The cubic root of 21724620 is about 279.0298910691.

The spelling of 21724620 in words is "twenty-one million, seven hundred twenty-four thousand, six hundred twenty".