21688460 has 12 divisors (see below), whose sum is σ = 45545808. Its totient is φ = 8675376.

The previous prime is 21688453. The next prime is 21688477. The reversal of 21688460 is 6488612.

It is a self number, because there is not a number n which added to its sum of digits gives 21688460.

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, 542192 + ... + 542231.

It is an arithmetic number, because the mean of its divisors is an integer number (3795484).

Almost surely, 2^21688460 is an apocalyptic number.

21688460 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21688460 is an abundant number, since it is smaller than the sum of its proper divisors (23857348).

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

21688460 is a wasteful number, since it uses less digits than its factorization.

21688460 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1084432 (or 1084430 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 35.

The square root of 21688460 is about 4657.0870724091. The cubic root of 21688460 is about 278.8749927087.

The spelling of 21688460 in words is "twenty-one million, six hundred eighty-eight thousand, four hundred sixty".