21120660 has 72 divisors (see below), whose sum is σ = 69896736. Its totient is φ = 5119680.

The previous prime is 21120637. The next prime is 21120661. The reversal of 21120660 is 6602112.

It is a happy number.

21120660 is a `hidden beast` number, since 2 + 1 + 1 + 2 + 0 + 660 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3354 + ... + 7313.

It is an arithmetic number, because the mean of its divisors is an integer number (970788).

Almost surely, 2^21120660 is an apocalyptic number.

21120660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21120660 is an abundant number, since it is smaller than the sum of its proper divisors (48776076).

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

21120660 is a wasteful number, since it uses less digits than its factorization.

21120660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10693 (or 10688 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21120660 is about 4595.7219237025. The cubic root of 21120660 is about 276.4198085135.

Adding to 21120660 its reverse (6602112), we get a palindrome (27722772).

The spelling of 21120660 in words is "twenty-one million, one hundred twenty thousand, six hundred sixty".