11661001211221 has 4 divisors (see below), whose sum is σ = 11674207328992. Its totient is φ = 11647795093452.

The previous prime is 11661001211179. The next prime is 11661001211273. The reversal of 11661001211221 is 12211210016611.

It is a happy number.

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 11661001211221 - 2⁹ = 11661001210709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11661001211021) 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, 6603057561 + ... + 6603059326.

It is an arithmetic number, because the mean of its divisors is an integer number (2918551832248).

Almost surely, 2^{11661001211221} is an apocalyptic number.

It is an amenable number.

11661001211221 is a deficient number, since it is larger than the sum of its proper divisors (13206117771).

11661001211221 is an equidigital number, since it uses as much as digits as its factorization.

11661001211221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13206117770.

The product of its (nonzero) digits is 288, while the sum is 25.

Adding to 11661001211221 its reverse (12211210016611), we get a palindrome (23872211227832).

The spelling of 11661001211221 in words is "eleven trillion, six hundred sixty-one billion, one million, two hundred eleven thousand, two hundred twenty-one".