21205217206 has 24 divisors (see below), whose sum is σ = 34015845600. Its totient is φ = 9911912832.

The previous prime is 21205217147. The next prime is 21205217207. The reversal of 21205217206 is 60271250212.

It is a super-2 number, since 2×21205217206² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205217207) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36990 + ... + 209233.

It is an arithmetic number, because the mean of its divisors is an integer number (1417326900).

Almost surely, 2^21205217206 is an apocalyptic number.

21205217206 is a deficient number, since it is larger than the sum of its proper divisors (12810628394).

21205217206 is a wasteful number, since it uses less digits than its factorization.

21205217206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246408 (or 246391 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 28.

Adding to 21205217206 its reverse (60271250212), we get a palindrome (81476467418).

The spelling of 21205217206 in words is "twenty-one billion, two hundred five million, two hundred seventeen thousand, two hundred six".