21063561 has 16 divisors (see below), whose sum is σ = 31031424. Its totient is φ = 12641024.

The previous prime is 21063529. The next prime is 21063569. The reversal of 21063561 is 16536012.

It is a cyclic number.

It is not a de Polignac number, because 21063561 - 2⁵ = 21063529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21063569) 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 15 ways as a sum of consecutive naturals, for example, 7806 + ... + 10151.

It is an arithmetic number, because the mean of its divisors is an integer number (1939464).

Almost surely, 2^21063561 is an apocalyptic number.

It is an amenable number.

21063561 is a deficient number, since it is larger than the sum of its proper divisors (9967863).

21063561 is a wasteful number, since it uses less digits than its factorization.

21063561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18000.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21063561 is about 4589.5055289214. The cubic root of 21063561 is about 276.1704864555.

Adding to 21063561 its reverse (16536012), we get a palindrome (37599573).

The spelling of 21063561 in words is "twenty-one million, sixty-three thousand, five hundred sixty-one".