21821986 has 8 divisors (see below), whose sum is σ = 34156224. Its totient is φ = 10436580.

The previous prime is 21821981. The next prime is 21822001. The reversal of 21821986 is 68912812.

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

It is not an unprimeable number, because it can be changed into a prime (21821981) 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, 237150 + ... + 237241.

It is an arithmetic number, because the mean of its divisors is an integer number (4269528).

Almost surely, 2^21821986 is an apocalyptic number.

21821986 is a deficient number, since it is larger than the sum of its proper divisors (12334238).

21821986 is a wasteful number, since it uses less digits than its factorization.

21821986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 474416.

The product of its digits is 13824, while the sum is 37.

The square root of 21821986 is about 4671.4008605556. The cubic root of 21821986 is about 279.4461244741.

The spelling of 21821986 in words is "twenty-one million, eight hundred twenty-one thousand, nine hundred eighty-six".