21666860 has 24 divisors (see below), whose sum is σ = 46611936. Its totient is φ = 8455040.

The previous prime is 21666829. The next prime is 21666863. The reversal of 21666860 is 6866612.

It is a self number, because there is not a number n which added to its sum of digits gives 21666860.

It is not an unprimeable number, because it can be changed into a prime (21666863) by changing a digit.

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, 12392 + ... + 14031.

It is an arithmetic number, because the mean of its divisors is an integer number (1942164).

Almost surely, 2^21666860 is an apocalyptic number.

21666860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21666860 is an abundant number, since it is smaller than the sum of its proper divisors (24945076).

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

21666860 is a wasteful number, since it uses less digits than its factorization.

21666860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26473 (or 26471 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 21666860 is about 4654.7674485413. The cubic root of 21666860 is about 278.7823827729.

It can be divided in two parts, 216 and 66860, that added together give a palindrome (67076).

The spelling of 21666860 in words is "twenty-one million, six hundred sixty-six thousand, eight hundred sixty".