21686830 has 24 divisors (see below), whose sum is σ = 42910056. Its totient is φ = 7885680.

The previous prime is 21686813. The next prime is 21686851. The reversal of 21686830 is 3868612.

It is a congruent number.

It is an unprimeable number.

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, 7752 + ... + 10171.

It is an arithmetic number, because the mean of its divisors is an integer number (1787919).

Almost surely, 2^21686830 is an apocalyptic number.

21686830 is a deficient number, since it is larger than the sum of its proper divisors (21223226).

21686830 is a wasteful number, since it uses less digits than its factorization.

21686830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17952 (or 17941 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 21686830 is about 4656.9120670247. The cubic root of 21686830 is about 278.8680062340.

It can be divided in two parts, 2168 and 6830, that added together give a palindrome (8998).

The spelling of 21686830 in words is "twenty-one million, six hundred eighty-six thousand, eight hundred thirty".