21723930 has 64 divisors (see below), whose sum is σ = 58924800. Its totient is φ = 5693760.

The previous prime is 21723913. The next prime is 21723931. The reversal of 21723930 is 3932712.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21723894 and 21723903.

It is not an unprimeable number, because it can be changed into a prime (21723931) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15811 + ... + 17129.

It is an arithmetic number, because the mean of its divisors is an integer number (920700).

Almost surely, 2^21723930 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21723930, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29462400).

21723930 is an abundant number, since it is smaller than the sum of its proper divisors (37200870).

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

21723930 is a wasteful number, since it uses less digits than its factorization.

21723930 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1396 (or 1390 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 21723930 is about 4660.8936911283. The cubic root of 21723930 is about 279.0269369298.

The spelling of 21723930 in words is "twenty-one million, seven hundred twenty-three thousand, nine hundred thirty".