21457760 has 48 divisors (see below), whose sum is σ = 51946272. Its totient is φ = 8371200.

The previous prime is 21457759. The next prime is 21457771. The reversal of 21457760 is 6775412.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a zygodrome in base 9.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4925 + ... + 8195.

It is an arithmetic number, because the mean of its divisors is an integer number (1082214).

Almost surely, 2^21457760 is an apocalyptic number.

21457760 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 21457760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25973136).

21457760 is an abundant number, since it is smaller than the sum of its proper divisors (30488512).

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

21457760 is a wasteful number, since it uses less digits than its factorization.

21457760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3327 (or 3319 counting only the distinct ones).

The product of its (nonzero) digits is 11760, while the sum is 32.

The square root of 21457760 is about 4632.2521520315. The cubic root of 21457760 is about 277.8826687726.

The spelling of 21457760 in words is "twenty-one million, four hundred fifty-seven thousand, seven hundred sixty".