21713280 has 128 divisors (see below), whose sum is σ = 71089920. Its totient is φ = 5634048.

The previous prime is 21713273. The next prime is 21713281. The reversal of 21713280 is 8231712.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21713280.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21713281) 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, 82429 + ... + 82691.

It is an arithmetic number, because the mean of its divisors is an integer number (555390).

Almost surely, 2^21713280 is an apocalyptic number.

21713280 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 21713280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35544960).

21713280 is an abundant number, since it is smaller than the sum of its proper divisors (49376640).

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

21713280 is a wasteful number, since it uses less digits than its factorization.

21713280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328 (or 316 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21713280 is about 4659.7510663124. The cubic root of 21713280 is about 278.9813324954.

Adding to 21713280 its reverse (8231712), we get a palindrome (29944992).

The spelling of 21713280 in words is "twenty-one million, seven hundred thirteen thousand, two hundred eighty".