2151991 has 2 divisors, whose sum is σ = 2151992. Its totient is φ = 2151990.

The previous prime is 2151977. The next prime is 2152001. The reversal of 2151991 is 1991512.

2151991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2151991 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2151971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1075995 + 1075996.

It is an arithmetic number, because the mean of its divisors is an integer number (1075996).

2^2151991 is an apocalyptic number.

2151991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2151991 is an equidigital number, since it uses as much as digits as its factorization.

2151991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 810, while the sum is 28.

The square root of 2151991 is about 1466.9665981201. The cubic root of 2151991 is about 129.1061162376.

The spelling of 2151991 in words is "two million, one hundred fifty-one thousand, nine hundred ninety-one".