21563963 has 4 divisors (see below), whose sum is σ = 21621240. Its totient is φ = 21506688.

The previous prime is 21563959. The next prime is 21564001. The reversal of 21563963 is 36936512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21563963 - 2² = 21563959 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21563923) 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 3 ways as a sum of consecutive naturals, for example, 28070 + ... + 28827.

It is an arithmetic number, because the mean of its divisors is an integer number (5405310).

Almost surely, 2^21563963 is an apocalyptic number.

21563963 is a deficient number, since it is larger than the sum of its proper divisors (57277).

21563963 is an equidigital number, since it uses as much as digits as its factorization.

21563963 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57276.

The product of its digits is 29160, while the sum is 35.

The square root of 21563963 is about 4643.7014331242. The cubic root of 21563963 is about 278.3403651595.

The spelling of 21563963 in words is "twenty-one million, five hundred sixty-three thousand, nine hundred sixty-three".