1211221001 has 4 divisors (see below), whose sum is σ = 1211802900. Its totient is φ = 1210639104.

The previous prime is 1211220991. The next prime is 1211221019. The reversal of 1211221001 is 1001221121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1001221121 = 61 ⋅16413461.

It can be written as a sum of positive squares in 2 ways, for example, as 1144062976 + 67158025 = 33824^2 + 8195^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211221001 - 2²² = 1207026697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1211221091) 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, 287816 + ... + 291993.

It is an arithmetic number, because the mean of its divisors is an integer number (302950725).

Almost surely, 2^1211221001 is an apocalyptic number.

It is an amenable number.

1211221001 is a deficient number, since it is larger than the sum of its proper divisors (581899).

1211221001 is an equidigital number, since it uses as much as digits as its factorization.

1211221001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 581898.

The product of its (nonzero) digits is 8, while the sum is 11.

The square root of 1211221001 is about 34802.6004919173. The cubic root of 1211221001 is about 1065.9605464080.

Adding to 1211221001 its reverse (1001221121), we get a palindrome (2212442122).

The spelling of 1211221001 in words is "one billion, two hundred eleven million, two hundred twenty-one thousand, one".