1221211211001 has 4 divisors (see below), whose sum is σ = 1628281614672. Its totient is φ = 814140807332.

The previous prime is 1221211210991. The next prime is 1221211211071. The reversal of 1221211211001 is 1001121121221.

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 1221211211001 - 2¹⁹ = 1221210686713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1221211211071) 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, 203535201831 + ... + 203535201836.

It is an arithmetic number, because the mean of its divisors is an integer number (407070403668).

Almost surely, 2^{1221211211001} is an apocalyptic number.

It is an amenable number.

1221211211001 is a deficient number, since it is larger than the sum of its proper divisors (407070403671).

1221211211001 is an equidigital number, since it uses as much as digits as its factorization.

1221211211001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407070403670.

The product of its (nonzero) digits is 16, while the sum is 15.

Adding to 1221211211001 its reverse (1001121121221), we get a palindrome (2222332332222).

The spelling of 1221211211001 in words is "one trillion, two hundred twenty-one billion, two hundred eleven million, two hundred eleven thousand, one".