21723270 has 64 divisors (see below), whose sum is σ = 57300480. Its totient is φ = 5246208.

The previous prime is 21723257. The next prime is 21723271. The reversal of 21723270 is 7232712.

It is a self number, because there is not a number n which added to its sum of digits gives 21723270.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21723271) 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, 12282 + ... + 13938.

It is an arithmetic number, because the mean of its divisors is an integer number (895320).

Almost surely, 2^21723270 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21723270, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28650240).

21723270 is an abundant number, since it is smaller than the sum of its proper divisors (35577210).

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

21723270 is a wasteful number, since it uses less digits than its factorization.

21723270 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1709.

The product of its (nonzero) digits is 1176, while the sum is 24.

The square root of 21723270 is about 4660.8228887183. The cubic root of 21723270 is about 279.0241111728.

Adding to 21723270 its reverse (7232712), we get a palindrome (28955982).

The spelling of 21723270 in words is "twenty-one million, seven hundred twenty-three thousand, two hundred seventy".