21563545 has 8 divisors (see below), whose sum is σ = 25935624. Its totient is φ = 17211264.

The previous prime is 21563539. The next prime is 21563557. The reversal of 21563545 is 54536512.

It can be written as a sum of positive squares in 4 ways, for example, as 6110784 + 15452761 = 2472^2 + 3931^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21563545 - 2⁵ = 21563513 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2434 + ... + 7003.

It is an arithmetic number, because the mean of its divisors is an integer number (3241953).

Almost surely, 2^21563545 is an apocalyptic number.

It is an amenable number.

21563545 is a deficient number, since it is larger than the sum of its proper divisors (4372079).

21563545 is an equidigital number, since it uses as much as digits as its factorization.

21563545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9899.

The product of its digits is 18000, while the sum is 31.

The square root of 21563545 is about 4643.6564257059. The cubic root of 21563545 is about 278.3385666802.

The spelling of 21563545 in words is "twenty-one million, five hundred sixty-three thousand, five hundred forty-five".