21821013664 has 24 divisors (see below), whose sum is σ = 43273706868. Its totient is φ = 10830865920.

The previous prime is 21821013647. The next prime is 21821013673. The reversal of 21821013664 is 46631012812.

It can be written as a sum of positive squares in 2 ways, for example, as 19751491600 + 2069522064 = 140540^2 + 45492^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2484327 + ... + 2493094.

Almost surely, 2^21821013664 is an apocalyptic number.

It is an amenable number.

21821013664 is a deficient number, since it is larger than the sum of its proper divisors (21452693204).

21821013664 is a wasteful number, since it uses less digits than its factorization.

21821013664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4977568 (or 4977560 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 34.

The spelling of 21821013664 in words is "twenty-one billion, eight hundred twenty-one million, thirteen thousand, six hundred sixty-four".