1211212109 has 4 divisors (see below), whose sum is σ = 1211318016. Its totient is φ = 1211106204.

The previous prime is 1211212063. The next prime is 1211212117. The reversal of 1211212109 is 9012121121.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1211212109 - 2⁸ = 1211211853 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 (1211212159) 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, 33389 + ... + 59474.

It is an arithmetic number, because the mean of its divisors is an integer number (302829504).

Almost surely, 2^1211212109 is an apocalyptic number.

It is an amenable number.

1211212109 is a deficient number, since it is larger than the sum of its proper divisors (105907).

1211212109 is an equidigital number, since it uses as much as digits as its factorization.

1211212109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105906.

The product of its (nonzero) digits is 72, while the sum is 20.

The square root of 1211212109 is about 34802.4727426084. The cubic root of 1211212109 is about 1065.9579378710.

The spelling of 1211212109 in words is "one billion, two hundred eleven million, two hundred twelve thousand, one hundred nine".