21757215816 has 128 divisors (see below), whose sum is σ = 69252710400. Its totient is φ = 6199951680.

The previous prime is 21757215803. The next prime is 21757215817. The reversal of 21757215816 is 61851275712.

21757215816 is a `hidden beast` number, since 2 + 17 + 57 + 2 + 1 + 581 + 6 = 666.

It is not an unprimeable number, because it can be changed into a prime (21757215817) 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, 560311 + ... + 597881.

It is an arithmetic number, because the mean of its divisors is an integer number (541036800).

Almost surely, 2^21757215816 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 21757215816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34626355200).

21757215816 is an abundant number, since it is smaller than the sum of its proper divisors (47495494584).

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

21757215816 is a wasteful number, since it uses less digits than its factorization.

21757215816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37976 (or 37966 counting only the distinct ones).

The product of its digits is 235200, while the sum is 45.

The spelling of 21757215816 in words is "twenty-one billion, seven hundred fifty-seven million, two hundred fifteen thousand, eight hundred sixteen".