21757320 has 96 divisors (see below), whose sum is σ = 76167000. Its totient is φ = 5354496.

The previous prime is 21757291. The next prime is 21757327. The reversal of 21757320 is 2375712.

It can be written as a sum of positive squares in 4 ways, for example, as 19342404 + 2414916 = 4398^2 + 1554^2 .

It is not an unprimeable number, because it can be changed into a prime (21757327) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2356 + ... + 7004.

Almost surely, 2^21757320 is an apocalyptic number.

21757320 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 21757320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38083500).

21757320 is an abundant number, since it is smaller than the sum of its proper divisors (54409680).

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

21757320 is a wasteful number, since it uses less digits than its factorization.

21757320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4679 (or 4672 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 21757320 is about 4664.4742469007. The cubic root of 21757320 is about 279.1698199193.

The spelling of 21757320 in words is "twenty-one million, seven hundred fifty-seven thousand, three hundred twenty".