21561850 has 12 divisors (see below), whose sum is σ = 40105134. Its totient is φ = 8624720.

The previous prime is 21561817. The next prime is 21561851. The reversal of 21561850 is 5816512.

It can be written as a sum of positive squares in 3 ways, for example, as 13682601 + 7879249 = 3699^2 + 2807^2 .

It is not an unprimeable number, because it can be changed into a prime (21561851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 215569 + ... + 215668.

Almost surely, 2^21561850 is an apocalyptic number.

21561850 is a deficient number, since it is larger than the sum of its proper divisors (18543284).

21561850 is a wasteful number, since it uses less digits than its factorization.

21561850 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 431249 (or 431244 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 21561850 is about 4643.4739150769. The cubic root of 21561850 is about 278.3312735653.

The spelling of 21561850 in words is "twenty-one million, five hundred sixty-one thousand, eight hundred fifty".