21756768 has 72 divisors (see below), whose sum is σ = 62808984. Its totient is φ = 6589440.

The previous prime is 21756733. The next prime is 21756769. The reversal of 21756768 is 86765712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21756769) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10680 + ... + 12552.

It is an arithmetic number, because the mean of its divisors is an integer number (872347).

Almost surely, 2^21756768 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21756768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31404492).

21756768 is an abundant number, since it is smaller than the sum of its proper divisors (41052216).

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

21756768 is a wasteful number, since it uses less digits than its factorization.

21756768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1908 (or 1889 counting only the distinct ones).

The product of its digits is 141120, while the sum is 42.

The square root of 21756768 is about 4664.4150758696. The cubic root of 21756768 is about 279.1674589814.

The spelling of 21756768 in words is "twenty-one million, seven hundred fifty-six thousand, seven hundred sixty-eight".