2157409 has 4 divisors (see below), whose sum is σ = 2167060. Its totient is φ = 2147760.

The previous prime is 2157401. The next prime is 2157413. The reversal of 2157409 is 9047512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1440000 + 717409 = 1200^2 + 847^2 .

It is a cyclic number.

It is not a de Polignac number, because 2157409 - 2³ = 2157401 is a prime.

It is a Duffinian number.

2157409 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (2157401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4482 + ... + 4939.

It is an arithmetic number, because the mean of its divisors is an integer number (541765).

2^2157409 is an apocalyptic number.

It is an amenable number.

2157409 is a deficient number, since it is larger than the sum of its proper divisors (9651).

2157409 is an equidigital number, since it uses as much as digits as its factorization.

2157409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9650.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 2157409 is about 1468.8121050699. The cubic root of 2157409 is about 129.2143742374.

The spelling of 2157409 in words is "two million, one hundred fifty-seven thousand, four hundred nine".