12921609 has 4 divisors (see below), whose sum is σ = 17228816. Its totient is φ = 8614404.

The previous prime is 12921599. The next prime is 12921611. The reversal of 12921609 is 90612921.

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.

It is not a de Polignac number, because 12921609 - 2¹¹ = 12919561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12921679) 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, 2153599 + ... + 2153604.

It is an arithmetic number, because the mean of its divisors is an integer number (4307204).

Almost surely, 2^12921609 is an apocalyptic number.

It is an amenable number.

12921609 is a deficient number, since it is larger than the sum of its proper divisors (4307207).

12921609 is an equidigital number, since it uses as much as digits as its factorization.

12921609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4307206.

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 12921609 is about 3594.6639620415. The cubic root of 12921609 is about 234.6598912885.

It can be divided in two parts, 12921 and 609, that added together give a triangular number (13530 = T₁₆₄).

The spelling of 12921609 in words is "twelve million, nine hundred twenty-one thousand, six hundred nine".