21788730 has 128 divisors (see below), whose sum is σ = 63452160. Its totient is φ = 5299200.

The previous prime is 21788729. The next prime is 21788743. The reversal of 21788730 is 3788712.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 215680 + ... + 215780.

It is an arithmetic number, because the mean of its divisors is an integer number (495720).

Almost surely, 2^21788730 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21788730, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31726080).

21788730 is an abundant number, since it is smaller than the sum of its proper divisors (41663430).

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

21788730 is a wasteful number, since it uses less digits than its factorization.

21788730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181 (or 175 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The square root of 21788730 is about 4667.8399715500. The cubic root of 21788730 is about 279.3040966863.

The spelling of 21788730 in words is "twenty-one million, seven hundred eighty-eight thousand, seven hundred thirty".