20721212 has 24 divisors (see below), whose sum is σ = 37153872. Its totient is φ = 10108800.

The previous prime is 20721209. The next prime is 20721223. The reversal of 20721212 is 21212702.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39512 + ... + 40032.

It is an arithmetic number, because the mean of its divisors is an integer number (1548078).

Almost surely, 2^20721212 is an apocalyptic number.

It is an amenable number.

20721212 is a deficient number, since it is larger than the sum of its proper divisors (16432660).

20721212 is a wasteful number, since it uses less digits than its factorization.

20721212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 749 (or 747 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 20721212 is about 4552.0557993065. The cubic root of 20721212 is about 274.6660939075. Note that the first 3 decimals are identical.

Adding to 20721212 its reverse (21212702), we get a palindrome (41933914).

The spelling of 20721212 in words is "twenty million, seven hundred twenty-one thousand, two hundred twelve".