1921609 has 4 divisors (see below), whose sum is σ = 1924560. Its totient is φ = 1918660.

The previous prime is 1921573. The next prime is 1921631. The reversal of 1921609 is 9061291.

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: 9061291 = 2467 ⋅3673.

It is a cyclic number.

It is not a de Polignac number, because 1921609 - 2⁷ = 1921481 is a prime.

It is a super-2 number, since 2×1921609² = 7385162297762, which contains 22 as substring.

It is a Duffinian number.

1921609 is a lucky number.

It is a plaindrome in base 7.

It is not an unprimeable number, because it can be changed into a prime (1921709) 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, 19 + ... + 1960.

It is an arithmetic number, because the mean of its divisors is an integer number (481140).

2^1921609 is an apocalyptic number.

It is an amenable number.

1921609 is a deficient number, since it is larger than the sum of its proper divisors (2951).

1921609 is an equidigital number, since it uses as much as digits as its factorization.

1921609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2950.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 1921609 is about 1386.2211223322. The cubic root of 1921609 is about 124.3240095519.

The spelling of 1921609 in words is "one million, nine hundred twenty-one thousand, six hundred nine".