21563530 has 16 divisors (see below), whose sum is σ = 40153320. Its totient is φ = 8327872.

The previous prime is 21563519. The next prime is 21563539. The reversal of 21563530 is 3536512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 12033961 + 9529569 = 3469^2 + 3087^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21563495 and 21563504.

It is not an unprimeable number, because it can be changed into a prime (21563539) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36889 + ... + 37468.

Almost surely, 2^21563530 is an apocalyptic number.

21563530 is a deficient number, since it is larger than the sum of its proper divisors (18589790).

21563530 is a wasteful number, since it uses less digits than its factorization.

21563530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74393.

The product of its (nonzero) digits is 2700, while the sum is 25.

The square root of 21563530 is about 4643.6548105991. The cubic root of 21563530 is about 278.3385021411.

The spelling of 21563530 in words is "twenty-one million, five hundred sixty-three thousand, five hundred thirty".