21749680 has 80 divisors (see below), whose sum is σ = 54684000. Its totient is φ = 8017920.

The previous prime is 21749677. The next prime is 21749713. The reversal of 21749680 is 8694712.

It is a tau number, because it is divible by the number of its divisors (80).

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, 62146 + ... + 62494.

It is an arithmetic number, because the mean of its divisors is an integer number (683550).

Almost surely, 2^21749680 is an apocalyptic number.

21749680 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 21749680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27342000).

21749680 is an abundant number, since it is smaller than the sum of its proper divisors (32934320).

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

21749680 is a wasteful number, since it uses less digits than its factorization.

21749680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 422 (or 416 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21749680 is about 4663.6552188171. The cubic root of 21749680 is about 279.1371396211.

The spelling of 21749680 in words is "twenty-one million, seven hundred forty-nine thousand, six hundred eighty".