21917280 has 192 divisors, whose sum is σ = 86220288. Its totient is φ = 4546560.

The previous prime is 21917227. The next prime is 21917281. The reversal of 21917280 is 8271912.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917281) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 36664 + ... + 37256.

It is an arithmetic number, because the mean of its divisors is an integer number (449064).

Almost surely, 2^21917280 is an apocalyptic number.

21917280 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 21917280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43110144).

21917280 is an abundant number, since it is smaller than the sum of its proper divisors (64303008).

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

21917280 is a wasteful number, since it uses less digits than its factorization.

21917280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 629 (or 621 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21917280 is about 4681.5894736724. The cubic root of 21917280 is about 279.8523030576.

The spelling of 21917280 in words is "twenty-one million, nine hundred seventeen thousand, two hundred eighty".