21361287816 has 64 divisors (see below), whose sum is σ = 64731182400. Its totient is φ = 6473116800.

The previous prime is 21361287793. The next prime is 21361287817. The reversal of 21361287816 is 61878216312.

21361287816 is a `hidden beast` number, since 2 + 1 + 361 + 287 + 8 + 1 + 6 = 666.

It is not an unprimeable number, because it can be changed into a prime (21361287817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4492845 + ... + 4497596.

It is an arithmetic number, because the mean of its divisors is an integer number (1011424725).

Almost surely, 2^21361287816 is an apocalyptic number.

It is an amenable number.

21361287816 is an abundant number, since it is smaller than the sum of its proper divisors (43369894584).

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

21361287816 is a wasteful number, since it uses less digits than its factorization.

21361287816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8990467 (or 8990457 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The spelling of 21361287816 in words is "twenty-one billion, three hundred sixty-one million, two hundred eighty-seven thousand, eight hundred sixteen".