21531201212 has 12 divisors (see below), whose sum is σ = 37837259040. Its totient is φ = 10720555776.

The previous prime is 21531201191. The next prime is 21531201221. The reversal of 21531201212 is 21210213512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11260133 + ... + 11262044.

It is an arithmetic number, because the mean of its divisors is an integer number (3153104920).

Almost surely, 2^21531201212 is an apocalyptic number.

It is an amenable number.

21531201212 is a deficient number, since it is larger than the sum of its proper divisors (16306057828).

21531201212 is a wasteful number, since it uses less digits than its factorization.

21531201212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22522420 (or 22522418 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 20.

Adding to 21531201212 its reverse (21210213512), we get a palindrome (42741414724).

The spelling of 21531201212 in words is "twenty-one billion, five hundred thirty-one million, two hundred one thousand, two hundred twelve".