21506368 has 28 divisors (see below), whose sum is σ = 45961300. Its totient is φ = 9925632.

The previous prime is 21506341. The next prime is 21506369. The reversal of 21506368 is 86360512.

It can be written as a sum of positive squares in 2 ways, for example, as 1364224 + 20142144 = 1168^2 + 4488^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506369) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12093 + ... + 13756.

It is an arithmetic number, because the mean of its divisors is an integer number (1641475).

Almost surely, 2^21506368 is an apocalyptic number.

It is an amenable number.

21506368 is an abundant number, since it is smaller than the sum of its proper divisors (24454932).

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

21506368 is a wasteful number, since it uses less digits than its factorization.

21506368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25874 (or 25864 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21506368 is about 4637.4958760089. The cubic root of 21506368 is about 278.0923385961.

The spelling of 21506368 in words is "twenty-one million, five hundred six thousand, three hundred sixty-eight".