1200011991 has 4 divisors (see below), whose sum is σ = 1600015992. Its totient is φ = 800007992.

The previous prime is 1200011987. The next prime is 1200012001. The reversal of 1200011991 is 1991100021.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1200011991 - 2² = 1200011987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1200011941) 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, 200001996 + ... + 200002001.

It is an arithmetic number, because the mean of its divisors is an integer number (400003998).

Almost surely, 2^1200011991 is an apocalyptic number.

1200011991 is a deficient number, since it is larger than the sum of its proper divisors (400004001).

1200011991 is an equidigital number, since it uses as much as digits as its factorization.

1200011991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400004000.

The product of its (nonzero) digits is 162, while the sum is 24.

The square root of 1200011991 is about 34641.1892261221. The cubic root of 1200011991 is about 1062.6621087094.

The spelling of 1200011991 in words is "one billion, two hundred million, eleven thousand, nine hundred ninety-one".