21111680 has 32 divisors (see below), whose sum is σ = 50471640. Its totient is φ = 8444416.

The previous prime is 21111617. The next prime is 21111683. The reversal of 21111680 is 8611112.

21111680 = 150² + 151² + ... + 405².

It is a tau number, because it is divible by the number of its divisors (32).

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 (21111683) 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 3 ways as a sum of consecutive naturals, for example, 15854 + ... + 17133.

Almost surely, 2^21111680 is an apocalyptic number.

21111680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21111680 is an abundant number, since it is smaller than the sum of its proper divisors (29359960).

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

21111680 is an equidigital number, since it uses as much as digits as its factorization.

21111680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33006 (or 32994 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 20.

The square root of 21111680 is about 4594.7448242530. The cubic root of 21111680 is about 276.3806272606.

Adding to 21111680 its reverse (8611112), we get a palindrome (29722792).

The spelling of 21111680 in words is "twenty-one million, one hundred eleven thousand, six hundred eighty".