20821212 has 72 divisors (see below), whose sum is σ = 56422912. Its totient is φ = 6706800.

The previous prime is 20821211. The next prime is 20821219. The reversal of 20821212 is 21212802.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821211) 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, 29787 + ... + 30477.

Almost surely, 2^20821212 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20821212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28211456).

20821212 is an abundant number, since it is smaller than the sum of its proper divisors (35601700).

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

20821212 is a wasteful number, since it uses less digits than its factorization.

20821212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 741 (or 727 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 20821212 is about 4563.0266271412. The cubic root of 20821212 is about 275.1072287071.

The spelling of 20821212 in words is "twenty million, eight hundred twenty-one thousand, two hundred twelve".