21730756 has 36 divisors (see below), whose sum is σ = 40805100. Its totient is φ = 10123200.

The previous prime is 21730747. The next prime is 21730759. The reversal of 21730756 is 65703712.

It can be written as a sum of positive squares in 2 ways, for example, as 12489156 + 9241600 = 3534^2 + 3040^2 .

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (21730759) 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, 145770 + ... + 145918.

It is an arithmetic number, because the mean of its divisors is an integer number (1133475).

Almost surely, 2^21730756 is an apocalyptic number.

It is an amenable number.

21730756 is a deficient number, since it is larger than the sum of its proper divisors (19074344).

21730756 is a wasteful number, since it uses less digits than its factorization.

21730756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 292 (or 271 counting only the distinct ones).

The product of its (nonzero) digits is 8820, while the sum is 31.

The square root of 21730756 is about 4661.6258966159. The cubic root of 21730756 is about 279.0561587513.

The spelling of 21730756 in words is "twenty-one million, seven hundred thirty thousand, seven hundred fifty-six".