21215440244 has 24 divisors (see below), whose sum is σ = 37499437248. Its totient is φ = 10501381440.

The previous prime is 21215440231. The next prime is 21215440307. The reversal of 21215440244 is 44204451212.

It is a happy number.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1731299 + ... + 1743509.

It is an arithmetic number, because the mean of its divisors is an integer number (1562476552).

Almost surely, 2^21215440244 is an apocalyptic number.

It is an amenable number.

21215440244 is a deficient number, since it is larger than the sum of its proper divisors (16283997004).

21215440244 is a wasteful number, since it uses less digits than its factorization.

21215440244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16535 (or 16533 counting only the distinct ones).

The product of its (nonzero) digits is 10240, while the sum is 29.

Adding to 21215440244 its reverse (44204451212), we get a palindrome (65419891456).

The spelling of 21215440244 in words is "twenty-one billion, two hundred fifteen million, four hundred forty thousand, two hundred forty-four".