21508165242 has 96 divisors (see below), whose sum is σ = 48961635840. Its totient is φ = 6815508480.

The previous prime is 21508165241. The next prime is 21508165249. The reversal of 21508165242 is 24256180512.

21508165242 is a `hidden beast` number, since 2 + 1 + 50 + 81 + 6 + 524 + 2 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 21508165197 and 21508165206.

It is not an unprimeable number, because it can be changed into a prime (21508165241) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 8093578 + ... + 8096234.

It is an arithmetic number, because the mean of its divisors is an integer number (510017040).

Almost surely, 2^21508165242 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21508165242, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24480817920).

21508165242 is an abundant number, since it is smaller than the sum of its proper divisors (27453470598).

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

21508165242 is a wasteful number, since it uses less digits than its factorization.

21508165242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2948 (or 2945 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 36.

The spelling of 21508165242 in words is "twenty-one billion, five hundred eight million, one hundred sixty-five thousand, two hundred forty-two".