21206560 has 24 divisors (see below), whose sum is σ = 50100876. Its totient is φ = 8482560.

The previous prime is 21206557. The next prime is 21206561. The reversal of 21206560 is 6560212.

21206560 is nontrivially palindromic in base 9.

It can be written as a sum of positive squares in 2 ways, for example, as 21049744 + 156816 = 4588^2 + 396^2 .

It is not an unprimeable number, because it can be changed into a prime (21206561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66111 + ... + 66430.

Almost surely, 2^21206560 is an apocalyptic number.

21206560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21206560 is an abundant number, since it is smaller than the sum of its proper divisors (28894316).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21206560 is a wasteful number, since it uses less digits than its factorization.

21206560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132556 (or 132548 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21206560 is about 4605.0580886673. The cubic root of 21206560 is about 276.7940446668.

Adding to 21206560 its reverse (6560212), we get a palindrome (27766772).

The spelling of 21206560 in words is "twenty-one million, two hundred six thousand, five hundred sixty".