2131605 has 48 divisors (see below), whose sum is σ = 4328064. Its totient is φ = 950400.

The previous prime is 2131603. The next prime is 2131609. The reversal of 2131605 is 5061312.

It is not a de Polignac number, because 2131605 - 2¹ = 2131603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2131601) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 21055 + ... + 21155.

It is an arithmetic number, because the mean of its divisors is an integer number (90168).

2^2131605 is an apocalyptic number.

It is an amenable number.

2131605 is an abundant number, since it is smaller than the sum of its proper divisors (2196459).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

2131605 is a wasteful number, since it uses less digits than its factorization.

2131605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 186 (or 183 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 2131605 is about 1460.0017123278. The cubic root of 2131605 is about 128.6971442324.

Adding to 2131605 its reverse (5061312), we get a palindrome (7192917).

It can be divided in two parts, 21 and 31605, that added together give a triangular number (31626 = T₂₅₁).

The spelling of 2131605 in words is "two million, one hundred thirty-one thousand, six hundred five".