21155111250 has 320 divisors, whose sum is σ = 66506711040. Its totient is φ = 4365216000.

The previous prime is 21155111249. The next prime is 21155111251. The reversal of 21155111250 is 5211155112.

It is an interprime number because it is at equal distance from previous prime (21155111249) and next prime (21155111251).

It is a self number, because there is not a number n which added to its sum of digits gives 21155111250.

It is not an unprimeable number, because it can be changed into a prime (21155111251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 16038091 + ... + 16039409.

It is an arithmetic number, because the mean of its divisors is an integer number (207833472).

Almost surely, 2^21155111250 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21155111250, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33253355520).

21155111250 is an abundant number, since it is smaller than the sum of its proper divisors (45351599790).

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

21155111250 is a wasteful number, since it uses less digits than its factorization.

21155111250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1411 (or 1396 counting only the distinct ones).

The product of its (nonzero) digits is 500, while the sum is 24.

Adding to 21155111250 its reverse (5211155112), we get a palindrome (26366266362).

The spelling of 21155111250 in words is "twenty-one billion, one hundred fifty-five million, one hundred eleven thousand, two hundred fifty".