21116840 has 16 divisors (see below), whose sum is σ = 47512980. Its totient is φ = 8446720.

The previous prime is 21116831. The next prime is 21116857. The reversal of 21116840 is 4861112.

It can be written as a sum of positive squares in 2 ways, for example, as 20921476 + 195364 = 4574^2 + 442^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 263921 + ... + 264000.

Almost surely, 2^21116840 is an apocalyptic number.

21116840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21116840 is an abundant number, since it is smaller than the sum of its proper divisors (26396140).

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

21116840 is a wasteful number, since it uses less digits than its factorization.

21116840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 527932 (or 527928 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 21116840 is about 4595.3063009989. The cubic root of 21116840 is about 276.4031425675.

Adding to 21116840 its reverse (4861112), we get a palindrome (25977952).

The spelling of 21116840 in words is "twenty-one million, one hundred sixteen thousand, eight hundred forty".