1644794509 has 4 divisors (see below), whose sum is σ = 1646390880. Its totient is φ = 1643198140.

The previous prime is 1644794491. The next prime is 1644794531. The reversal of 1644794509 is 9054974461.

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: 9054974461 = 13 ⋅696536497.

It is a cyclic number.

It is not a de Polignac number, because 1644794509 - 2⁷ = 1644794381 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644794549) 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, 796639 + ... + 798700.

It is an arithmetic number, because the mean of its divisors is an integer number (411597720).

Almost surely, 2^1644794509 is an apocalyptic number.

It is an amenable number.

1644794509 is a deficient number, since it is larger than the sum of its proper divisors (1596371).

1644794509 is a wasteful number, since it uses less digits than its factorization.

1644794509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1596370.

The product of its (nonzero) digits is 1088640, while the sum is 49.

The square root of 1644794509 is about 40556.0662416857. The cubic root of 1644794509 is about 1180.4217847244.

The spelling of 1644794509 in words is "one billion, six hundred forty-four million, seven hundred ninety-four thousand, five hundred nine".