21680090 has 8 divisors (see below), whose sum is σ = 39024180. Its totient is φ = 8672032.

The previous prime is 21680077. The next prime is 21680093. The reversal of 21680090 is 9008612.

It can be written as a sum of positive squares in 2 ways, for example, as 19811401 + 1868689 = 4451^2 + 1367^2 .

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21680093) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1083995 + ... + 1084014.

Almost surely, 2^21680090 is an apocalyptic number.

21680090 is a deficient number, since it is larger than the sum of its proper divisors (17344090).

21680090 is a wasteful number, since it uses less digits than its factorization.

21680090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2168016.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21680090 is about 4656.1883552966. The cubic root of 21680090 is about 278.8391136587.

The spelling of 21680090 in words is "twenty-one million, six hundred eighty thousand, ninety".