21240244521 has 40 divisors (see below), whose sum is σ = 32270456064. Its totient is φ = 13920595200.

The previous prime is 21240244517. The next prime is 21240244523. The reversal of 21240244521 is 12544204212.

It is a happy number.

21240244521 is a `hidden beast` number, since 212 + 4 + 0 + 2 + 445 + 2 + 1 = 666.

It is not a de Polignac number, because 21240244521 - 2² = 21240244517 is a prime.

It is a super-2 number, since 2×21240244521² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21240244523) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1177456 + ... + 1195358.

Almost surely, 2^21240244521 is an apocalyptic number.

It is an amenable number.

21240244521 is a deficient number, since it is larger than the sum of its proper divisors (11030211543).

21240244521 is a wasteful number, since it uses less digits than its factorization.

21240244521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18163 (or 18154 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 27.

Adding to 21240244521 its reverse (12544204212), we get a palindrome (33784448733).

The spelling of 21240244521 in words is "twenty-one billion, two hundred forty million, two hundred forty-four thousand, five hundred twenty-one".