21785982 has 8 divisors (see below), whose sum is σ = 43571976. Its totient is φ = 7261992.

The previous prime is 21785977. The next prime is 21785983. The reversal of 21785982 is 28958712.

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

21785982 is an admirable number.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21785983) 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, 1815493 + ... + 1815504.

It is an arithmetic number, because the mean of its divisors is an integer number (5446497).

Almost surely, 2^21785982 is an apocalyptic number.

21785982 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21785982 is a wasteful number, since it uses less digits than its factorization.

21785982 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3631002.

The product of its digits is 80640, while the sum is 42.

The square root of 21785982 is about 4667.5456077043. The cubic root of 21785982 is about 279.2923542255.

The spelling of 21785982 in words is "twenty-one million, seven hundred eighty-five thousand, nine hundred eighty-two".