21712320 has 224 divisors, whose sum is σ = 87782400. Its totient is φ = 4948992.

The previous prime is 21712319. The next prime is 21712331. The reversal of 21712320 is 2321712.

It is a tau number, because it is divible by the number of its divisors (224).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 21712293 and 21712302.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 60301 + ... + 60659.

Almost surely, 2^21712320 is an apocalyptic number.

21712320 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 21712320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43891200).

21712320 is an abundant number, since it is smaller than the sum of its proper divisors (66070080).

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

21712320 is a wasteful number, since it uses less digits than its factorization.

21712320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392 (or 376 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21712320 is about 4659.6480553793. The cubic root of 21712320 is about 278.9772209406.

The spelling of 21712320 in words is "twenty-one million, seven hundred twelve thousand, three hundred twenty".