21163860 has 36 divisors (see below), whose sum is σ = 64197588. Its totient is φ = 5643648.

The previous prime is 21163859. The next prime is 21163867. The reversal of 21163860 is 6836112.

21163860 is a `hidden beast` number, since 21 + 1 + 638 + 6 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 15023376 + 6140484 = 3876^2 + 2478^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21163867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 58609 + ... + 58968.

Almost surely, 2^21163860 is an apocalyptic number.

21163860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21163860 is an abundant number, since it is smaller than the sum of its proper divisors (43033728).

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

21163860 is a wasteful number, since it uses less digits than its factorization.

21163860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117592 (or 117587 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21163860 is about 4600.4195460849. The cubic root of 21163860 is about 276.6081423282.

Adding to 21163860 its reverse (6836112), we get a palindrome (27999972).

It can be divided in two parts, 211638 and 60, that multiplied together give a triangular number (12698280 = T₅₀₃₉).

The spelling of 21163860 in words is "twenty-one million, one hundred sixty-three thousand, eight hundred sixty".