21115213056 has 288 divisors, whose sum is σ = 71706136320. Its totient is φ = 6003818496.

The previous prime is 21115213051. The next prime is 21115213061. The reversal of 21115213056 is 65031251112.

It is an interprime number because it is at equal distance from previous prime (21115213051) and next prime (21115213061).

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21115213051) 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, 11272536 + ... + 11274408.

It is an arithmetic number, because the mean of its divisors is an integer number (248979640).

Almost surely, 2^21115213056 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 21115213056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35853068160).

21115213056 is an abundant number, since it is smaller than the sum of its proper divisors (50590923264).

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

21115213056 is a wasteful number, since it uses less digits than its factorization.

21115213056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2138 (or 2118 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

Adding to 21115213056 its reverse (65031251112), we get a palindrome (86146464168).

The spelling of 21115213056 in words is "twenty-one billion, one hundred fifteen million, two hundred thirteen thousand, fifty-six".