21115860 has 24 divisors (see below), whose sum is σ = 59124576. Its totient is φ = 5630880.

The previous prime is 21115837. The next prime is 21115879. The reversal of 21115860 is 6851112.

It is a self number, because there is not a number n which added to its sum of digits gives 21115860.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 175906 + ... + 176025.

It is an arithmetic number, because the mean of its divisors is an integer number (2463524).

Almost surely, 2^21115860 is an apocalyptic number.

21115860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21115860 is an abundant number, since it is smaller than the sum of its proper divisors (38008716).

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

21115860 is a wasteful number, since it uses less digits than its factorization.

21115860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351943 (or 351941 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 21115860 is about 4595.1996692200. The cubic root of 21115860 is about 276.3988666867.

Adding to 21115860 its reverse (6851112), we get a palindrome (27966972).

The spelling of 21115860 in words is "twenty-one million, one hundred fifteen thousand, eight hundred sixty".