2138409 has 36 divisors (see below), whose sum is σ = 3879876. Its totient is φ = 1124928.

The previous prime is 2138407. The next prime is 2138419. The reversal of 2138409 is 9048312.

It can be written as a sum of positive squares in 2 ways, for example, as 705600 + 1432809 = 840^2 + 1197^2 .

It is not a de Polignac number, because 2138409 - 2¹ = 2138407 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2138401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 5547 + ... + 5919.

2^2138409 is an apocalyptic number.

It is an amenable number.

2138409 is a deficient number, since it is larger than the sum of its proper divisors (1741467).

2138409 is a wasteful number, since it uses less digits than its factorization.

2138409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406 (or 396 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 2138409 is about 1462.3299901185. The cubic root of 2138409 is about 128.8339308841.

Subtracting 2138409 from its reverse (9048312), we obtain a triangular number (6909903 = T₃₇₁₇).

The spelling of 2138409 in words is "two million, one hundred thirty-eight thousand, four hundred nine".