2151891 has 12 divisors (see below), whose sum is σ = 3552432. Its totient is φ = 1229616.

The previous prime is 2151869. The next prime is 2151899. The reversal of 2151891 is 1981512.

2151891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 2151891 - 2⁶ = 2151827 is a prime.

2151891 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (2151899) 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 in 11 ways as a sum of consecutive naturals, for example, 17016 + ... + 17141.

It is an arithmetic number, because the mean of its divisors is an integer number (296036).

2^2151891 is an apocalyptic number.

2151891 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

2151891 is a deficient number, since it is larger than the sum of its proper divisors (1400541).

2151891 is a wasteful number, since it uses less digits than its factorization.

2151891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34170 (or 34167 counting only the distinct ones).

The product of its digits is 720, while the sum is 27.

The square root of 2151891 is about 1466.9325137851. The cubic root of 2151891 is about 129.1041164133.

It can be divided in two parts, 21518 and 91, that added together give a square (21609 = 147²).

The spelling of 2151891 in words is "two million, one hundred fifty-one thousand, eight hundred ninety-one".