21756648 has 32 divisors (see below), whose sum is σ = 54633600. Its totient is φ = 7219968.

The previous prime is 21756613. The next prime is 21756649. The reversal of 21756648 is 84665712.

It is not an unprimeable number, because it can be changed into a prime (21756649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3840 + ... + 7632.

It is an arithmetic number, because the mean of its divisors is an integer number (1707300).

Almost surely, 2^21756648 is an apocalyptic number.

It is an amenable number.

21756648 is an abundant number, since it is smaller than the sum of its proper divisors (32876952).

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

21756648 is a wasteful number, since it uses less digits than its factorization.

21756648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4041 (or 4037 counting only the distinct ones).

The product of its digits is 80640, while the sum is 39.

The square root of 21756648 is about 4664.4022125027. The cubic root of 21756648 is about 279.1669457288.

It can be divided in two parts, 217 and 56648, that added together give a palindrome (56865).

The spelling of 21756648 in words is "twenty-one million, seven hundred fifty-six thousand, six hundred forty-eight".