20121121991 has 2 divisors, whose sum is σ = 20121121992. Its totient is φ = 20121121990.

The previous prime is 20121121949. The next prime is 20121122011. The reversal of 20121121991 is 19912112102.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20121121991 - 2⁶ = 20121121927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20121121291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10060560995 + 10060560996.

It is an arithmetic number, because the mean of its divisors is an integer number (10060560996).

Almost surely, 2^20121121991 is an apocalyptic number.

20121121991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20121121991 is an equidigital number, since it uses as much as digits as its factorization.

20121121991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 29.

The spelling of 20121121991 in words is "twenty billion, one hundred twenty-one million, one hundred twenty-one thousand, nine hundred ninety-one".