21006560 has 48 divisors (see below), whose sum is σ = 52554096. Its totient is φ = 7907328.

The previous prime is 21006551. The next prime is 21006563. The reversal of 21006560 is 6560012.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1142 + ... + 6581.

It is an arithmetic number, because the mean of its divisors is an integer number (1094877).

Almost surely, 2^21006560 is an apocalyptic number.

21006560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21006560 is an abundant number, since it is smaller than the sum of its proper divisors (31547536).

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

21006560 is a wasteful number, since it uses less digits than its factorization.

21006560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7755 (or 7747 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21006560 is about 4583.2913937475. The cubic root of 21006560 is about 275.9211424927.

Adding to 21006560 its reverse (6560012), we get a palindrome (27566572).

The spelling of 21006560 in words is "twenty-one million, six thousand, five hundred sixty".