21722320 has 80 divisors (see below), whose sum is σ = 54996480. Its totient is φ = 7948800.

The previous prime is 21722317. The next prime is 21722321. The reversal of 21722320 is 2322712.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21722321) 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, 46890 + ... + 47350.

It is an arithmetic number, because the mean of its divisors is an integer number (687456).

Almost surely, 2^21722320 is an apocalyptic number.

21722320 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 21722320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27498240).

21722320 is an abundant number, since it is smaller than the sum of its proper divisors (33274160).

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

21722320 is a wasteful number, since it uses less digits than its factorization.

21722320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 524 (or 518 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21722320 is about 4660.7209742700. The cubic root of 21722320 is about 279.0200436947.

The spelling of 21722320 in words is "twenty-one million, seven hundred twenty-two thousand, three hundred twenty".