21123560 has 32 divisors (see below), whose sum is σ = 47692800. Its totient is φ = 8420160.

The previous prime is 21123533. The next prime is 21123589. The reversal of 21123560 is 6532112.

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

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, 13625 + ... + 15095.

It is an arithmetic number, because the mean of its divisors is an integer number (1490400).

Almost surely, 2^21123560 is an apocalyptic number.

21123560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21123560 is an abundant number, since it is smaller than the sum of its proper divisors (26569240).

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

21123560 is a wasteful number, since it uses less digits than its factorization.

21123560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1841 (or 1837 counting only the distinct ones).

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

The square root of 21123560 is about 4596.0374236945. The cubic root of 21123560 is about 276.4324593296.

Adding to 21123560 its reverse (6532112), we get a palindrome (27655672).

The spelling of 21123560 in words is "twenty-one million, one hundred twenty-three thousand, five hundred sixty".