1644881649 has 4 divisors (see below), whose sum is σ = 2193175536. Its totient is φ = 1096587764.

The previous prime is 1644881647. The next prime is 1644881717. The reversal of 1644881649 is 9461884461.

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 a cyclic number.

It is not a de Polignac number, because 1644881649 - 2¹ = 1644881647 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1644881647) 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, 274146939 + ... + 274146944.

It is an arithmetic number, because the mean of its divisors is an integer number (548293884).

Almost surely, 2^1644881649 is an apocalyptic number.

It is an amenable number.

1644881649 is a deficient number, since it is larger than the sum of its proper divisors (548293887).

1644881649 is an equidigital number, since it uses as much as digits as its factorization.

1644881649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 548293886.

The product of its digits is 1327104, while the sum is 51.

The square root of 1644881649 is about 40557.1405426961. The cubic root of 1644881649 is about 1180.4426303148.

The spelling of 1644881649 in words is "one billion, six hundred forty-four million, eight hundred eighty-one thousand, six hundred forty-nine".