21012443505 has 48 divisors (see below), whose sum is σ = 36884300544. Its totient is φ = 11065161600.

The previous prime is 21012443489. The next prime is 21012443509. The reversal of 21012443505 is 50534421012.

21012443505 is a `hidden beast` number, since 210 + 1 + 2 + 443 + 5 + 0 + 5 = 666.

It is not a de Polignac number, because 21012443505 - 2⁴ = 21012443489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21012443509) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1125507 + ... + 1144023.

It is an arithmetic number, because the mean of its divisors is an integer number (768422928).

Almost surely, 2^21012443505 is an apocalyptic number.

It is an amenable number.

21012443505 is a deficient number, since it is larger than the sum of its proper divisors (15871857039).

21012443505 is a wasteful number, since it uses less digits than its factorization.

21012443505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18846 (or 18843 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

Adding to 21012443505 its reverse (50534421012), we get a palindrome (71546864517).

The spelling of 21012443505 in words is "twenty-one billion, twelve million, four hundred forty-three thousand, five hundred five".