21205413516 has 96 divisors (see below), whose sum is σ = 57414389760. Its totient is φ = 5966049600.

The previous prime is 21205413499. The next prime is 21205413557. The reversal of 21205413516 is 61531450212.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6505095 + ... + 6508353.

It is an arithmetic number, because the mean of its divisors is an integer number (598066560).

Almost surely, 2^21205413516 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 21205413516, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28707194880).

21205413516 is an abundant number, since it is smaller than the sum of its proper divisors (36208976244).

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

21205413516 is a wasteful number, since it uses less digits than its factorization.

21205413516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4435 (or 4433 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 30.

Adding to 21205413516 its reverse (61531450212), we get a palindrome (82736863728).

The spelling of 21205413516 in words is "twenty-one billion, two hundred five million, four hundred thirteen thousand, five hundred sixteen".