1021201021991 has 2 divisors, whose sum is σ = 1021201021992. Its totient is φ = 1021201021990.

The previous prime is 1021201021979. The next prime is 1021201022099. The reversal of 1021201021991 is 1991201021201.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1021201021991 - 2¹⁴ = 1021201005607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1021201021901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510600510995 + 510600510996.

It is an arithmetic number, because the mean of its divisors is an integer number (510600510996).

Almost surely, 2^{1021201021991} is an apocalyptic number.

1021201021991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1021201021991 is an equidigital number, since it uses as much as digits as its factorization.

1021201021991 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 1021201021991 in words is "one trillion, twenty-one billion, two hundred one million, twenty-one thousand, nine hundred ninety-one".