21579618816 has 360 divisors, whose sum is σ = 74809747584. Its totient is φ = 5964779520.

The previous prime is 21579618811. The next prime is 21579618857. The reversal of 21579618816 is 61881697512.

It is a happy number.

21579618816 is a `hidden beast` number, since 2 + 1 + 5 + 7 + 9 + 618 + 8 + 16 = 666.

It is a super-2 number, since 2×21579618816² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21579618811) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 6998011 + ... + 7001093.

Almost surely, 2^21579618816 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 21579618816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37404873792).

21579618816 is an abundant number, since it is smaller than the sum of its proper divisors (53230128768).

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

21579618816 is a wasteful number, since it uses less digits than its factorization.

21579618816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3152 (or 3126 counting only the distinct ones).

The product of its digits is 1451520, while the sum is 54.

The spelling of 21579618816 in words is "twenty-one billion, five hundred seventy-nine million, six hundred eighteen thousand, eight hundred sixteen".