20101321991 has 2 divisors, whose sum is σ = 20101321992. Its totient is φ = 20101321990.

The previous prime is 20101321987. The next prime is 20101321993. The reversal of 20101321991 is 19912310102.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20101321991 - 2² = 20101321987 is a prime.

It is a Sophie Germain prime.

Together with 20101321993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20101321993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10050660995 + 10050660996.

It is an arithmetic number, because the mean of its divisors is an integer number (10050660996).

Almost surely, 2^20101321991 is an apocalyptic number.

20101321991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20101321991 is an equidigital number, since it uses as much as digits as its factorization.

20101321991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 29.

The spelling of 20101321991 in words is "twenty billion, one hundred one million, three hundred twenty-one thousand, nine hundred ninety-one".