2609821 has 4 divisors (see below), whose sum is σ = 2747200. Its totient is φ = 2472444.

The previous prime is 2609813. The next prime is 2609899. The reversal of 2609821 is 1289062.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1289062 = 2 ⋅644531.

It is a cyclic number.

It is not a de Polignac number, because 2609821 - 2³ = 2609813 is a prime.

It is a super-2 number, since 2×2609821² = 13622331304082, which contains 22 as substring.

It is a Duffinian number.

2609821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 2609821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2609021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68661 + ... + 68698.

It is an arithmetic number, because the mean of its divisors is an integer number (686800).

2^2609821 is an apocalyptic number.

It is an amenable number.

2609821 is a deficient number, since it is larger than the sum of its proper divisors (137379).

2609821 is a wasteful number, since it uses less digits than its factorization.

2609821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137378.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 2609821 is about 1615.4940420812. The cubic root of 2609821 is about 137.6798044423.

The spelling of 2609821 in words is "two million, six hundred nine thousand, eight hundred twenty-one".