102021991 has 2 divisors, whose sum is σ = 102021992. Its totient is φ = 102021990.

The previous prime is 102021989. The next prime is 102022003. The reversal of 102021991 is 199120201.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 102021991 - 2¹ = 102021989 is a prime.

Together with 102021989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (102021911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 51010995 + 51010996.

It is an arithmetic number, because the mean of its divisors is an integer number (51010996).

Almost surely, 2^102021991 is an apocalyptic number.

102021991 is a deficient number, since it is larger than the sum of its proper divisors (1).

102021991 is an equidigital number, since it uses as much as digits as its factorization.

102021991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 25.

The square root of 102021991 is about 10100.5935964180. The cubic root of 102021991 is about 467.2664485864.

The spelling of 102021991 in words is "one hundred two million, twenty-one thousand, nine hundred ninety-one".