21221100012 has 96 divisors (see below), whose sum is σ = 57511157760. Its totient is φ = 5964678720.

The previous prime is 21221100007. The next prime is 21221100013. The reversal of 21221100012 is 21000112212.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is not an unprimeable number, because it can be changed into a prime (21221100013) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5125039 + ... + 5129177.

It is an arithmetic number, because the mean of its divisors is an integer number (599074560).

Almost surely, 2^21221100012 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 21221100012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28755578880).

21221100012 is an abundant number, since it is smaller than the sum of its proper divisors (36290057748).

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

21221100012 is a wasteful number, since it uses less digits than its factorization.

21221100012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5131 (or 5129 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21221100012 its reverse (21000112212), we get a palindrome (42221212224).

The spelling of 21221100012 in words is "twenty-one billion, two hundred twenty-one million, one hundred thousand, twelve".