12205721 has 4 divisors (see below), whose sum is σ = 13315344. Its totient is φ = 11096100.

The previous prime is 12205691. The next prime is 12205747. The reversal of 12205721 is 12750221.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 12205721 - 2¹⁴ = 12189337 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 12205693 and 12205702.

It is not an unprimeable number, because it can be changed into a prime (12205751) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 554795 + ... + 554816.

It is an arithmetic number, because the mean of its divisors is an integer number (3328836).

Almost surely, 2^12205721 is an apocalyptic number.

12205721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

12205721 is a deficient number, since it is larger than the sum of its proper divisors (1109623).

12205721 is a wasteful number, since it uses less digits than its factorization.

12205721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1109622.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 12205721 is about 3493.6687020953. The cubic root of 12205721 is about 230.2437302864.

Adding to 12205721 its reverse (12750221), we get a palindrome (24955942).

The spelling of 12205721 in words is "twelve million, two hundred five thousand, seven hundred twenty-one".