1211001001 has 16 divisors (see below), whose sum is σ = 1474212096. Its totient is φ = 971076096.

The previous prime is 1211000971. The next prime is 1211001023. The reversal of 1211001001 is 1001001121.

It is a cyclic number.

It is not a de Polignac number, because 1211001001 - 2²⁷ = 1076783273 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (7).

It is not an unprimeable number, because it can be changed into a prime (1211001031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10596 + ... + 50341.

It is an arithmetic number, because the mean of its divisors is an integer number (92138256).

Almost surely, 2^1211001001 is an apocalyptic number.

It is an amenable number.

1211001001 is a deficient number, since it is larger than the sum of its proper divisors (263211095).

1211001001 is a wasteful number, since it uses less digits than its factorization.

1211001001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61128.

The product of its (nonzero) digits is 2, while the sum is 7.

The square root of 1211001001 is about 34799.4396650291. The cubic root of 1211001001 is about 1065.8960039560.

Adding to 1211001001 its reverse (1001001121), we get a palindrome (2212002122).

It can be divided in two parts, 121 and 1001001, that multiplied together give a palindrome (121121121).

The spelling of 1211001001 in words is "one billion, two hundred eleven million, one thousand, one".