20821986 has 48 divisors (see below), whose sum is σ = 48016800. Its totient is φ = 6502464.

The previous prime is 20821981. The next prime is 20822017. The reversal of 20821986 is 68912802.

It is a self number, because there is not a number n which added to its sum of digits gives 20821986.

It is not an unprimeable number, because it can be changed into a prime (20821981) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36310 + ... + 36878.

It is an arithmetic number, because the mean of its divisors is an integer number (1000350).

Almost surely, 2^20821986 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20821986, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24008400).

20821986 is an abundant number, since it is smaller than the sum of its proper divisors (27194814).

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

20821986 is a wasteful number, since it uses less digits than its factorization.

20821986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 703 (or 700 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 20821986 is about 4563.1114384814. Note that the first 3 decimals coincide. The cubic root of 20821986 is about 275.1106375762.

The spelling of 20821986 in words is "twenty million, eight hundred twenty-one thousand, nine hundred eighty-six".