20121199991 has 2 divisors, whose sum is σ = 20121199992. Its totient is φ = 20121199990.

The previous prime is 20121199981. The next prime is 20121199997. The reversal of 20121199991 is 19999112102.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20121199991 - 2¹⁰ = 20121198967 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20121199997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10060599995 + 10060599996.

It is an arithmetic number, because the mean of its divisors is an integer number (10060599996).

Almost surely, 2^20121199991 is an apocalyptic number.

20121199991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20121199991 is an equidigital number, since it uses as much as digits as its factorization.

20121199991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 26244, while the sum is 44.

The spelling of 20121199991 in words is "twenty billion, one hundred twenty-one million, one hundred ninety-nine thousand, nine hundred ninety-one".