21788660 has 48 divisors (see below), whose sum is σ = 47803392. Its totient is φ = 8332800.

The previous prime is 21788653. The next prime is 21788677. The reversal of 21788660 is 6688712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 69905 + ... + 70215.

It is an arithmetic number, because the mean of its divisors is an integer number (995904).

Almost surely, 2^21788660 is an apocalyptic number.

21788660 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 21788660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23901696).

21788660 is an abundant number, since it is smaller than the sum of its proper divisors (26014732).

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

21788660 is a wasteful number, since it uses less digits than its factorization.

21788660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 464 (or 462 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 38.

The square root of 21788660 is about 4667.8324734292. The cubic root of 21788660 is about 279.3037975820.

The spelling of 21788660 in words is "twenty-one million, seven hundred eighty-eight thousand, six hundred sixty".