102001991 has 8 divisors (see below), whose sum is σ = 125541024. Its totient is φ = 80704800.

The previous prime is 102001981. The next prime is 102001993. The reversal of 102001991 is 199100201.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 102001991 - 2⁶ = 102001927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (102001993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 560360 + ... + 560541.

It is an arithmetic number, because the mean of its divisors is an integer number (15692628).

Almost surely, 2^102001991 is an apocalyptic number.

102001991 is a deficient number, since it is larger than the sum of its proper divisors (23539033).

102001991 is a wasteful number, since it uses less digits than its factorization.

102001991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1120921.

The product of its (nonzero) digits is 162, while the sum is 23.

The square root of 102001991 is about 10099.6035070690. The cubic root of 102001991 is about 467.2359128832.

The spelling of 102001991 in words is "one hundred two million, one thousand, nine hundred ninety-one".