1212098991 has 4 divisors (see below), whose sum is σ = 1616131992. Its totient is φ = 808065992.

The previous prime is 1212098983. The next prime is 1212099001. The reversal of 1212098991 is 1998902121.

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 1212098991 - 2³ = 1212098983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1212098911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 202016496 + ... + 202016501.

It is an arithmetic number, because the mean of its divisors is an integer number (404032998).

Almost surely, 2^1212098991 is an apocalyptic number.

1212098991 is a deficient number, since it is larger than the sum of its proper divisors (404033001).

1212098991 is an equidigital number, since it uses as much as digits as its factorization.

1212098991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404033000.

The product of its (nonzero) digits is 23328, while the sum is 42.

The square root of 1212098991 is about 34815.2120631198. The cubic root of 1212098991 is about 1066.2180487277.

It can be divided in two parts, 12120 and 98991, that added together give a palindrome (111111).

The spelling of 1212098991 in words is "one billion, two hundred twelve million, ninety-eight thousand, nine hundred ninety-one".