21688190 has 8 divisors (see below), whose sum is σ = 39038760. Its totient is φ = 8675272.

The previous prime is 21688187. The next prime is 21688213. The reversal of 21688190 is 9188612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21688190² = 940755170952200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21688190.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1084400 + ... + 1084419.

It is an arithmetic number, because the mean of its divisors is an integer number (4879845).

Almost surely, 2^21688190 is an apocalyptic number.

21688190 is a deficient number, since it is larger than the sum of its proper divisors (17350570).

21688190 is a wasteful number, since it uses less digits than its factorization.

21688190 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2168826.

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 21688190 is about 4657.0580842416. The cubic root of 21688190 is about 278.8738354640.

The spelling of 21688190 in words is "twenty-one million, six hundred eighty-eight thousand, one hundred ninety".