21002112156 has 72 divisors (see below), whose sum is σ = 53503647120. Its totient is φ = 6403509504.

The previous prime is 21002112143. The next prime is 21002112163. The reversal of 21002112156 is 65121120012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 42040 + ... + 209216.

It is an arithmetic number, because the mean of its divisors is an integer number (743106210).

Almost surely, 2^21002112156 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 21002112156, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26751823560).

21002112156 is an abundant number, since it is smaller than the sum of its proper divisors (32501534964).

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

21002112156 is a wasteful number, since it uses less digits than its factorization.

21002112156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167251 (or 167230 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 21.

Adding to 21002112156 its reverse (65121120012), we get a palindrome (86123232168).

The spelling of 21002112156 in words is "twenty-one billion, two million, one hundred twelve thousand, one hundred fifty-six".