1640997649 has 4 divisors (see below), whose sum is σ = 1641110080. Its totient is φ = 1640885220.

The previous prime is 1640997599. The next prime is 1640997697. The reversal of 1640997649 is 9467990461.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1640997649 - 2⁷ = 1640997521 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1640997649.

It is not an unprimeable number, because it can be changed into a prime (1640997049) 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, 30357 + ... + 64834.

It is an arithmetic number, because the mean of its divisors is an integer number (410277520).

Almost surely, 2^1640997649 is an apocalyptic number.

It is an amenable number.

1640997649 is a deficient number, since it is larger than the sum of its proper divisors (112431).

1640997649 is an equidigital number, since it uses as much as digits as its factorization.

1640997649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112430.

The product of its (nonzero) digits is 2939328, while the sum is 55.

The square root of 1640997649 is about 40509.2291829899. The cubic root of 1640997649 is about 1179.5127857892.

The spelling of 1640997649 in words is "one billion, six hundred forty million, nine hundred ninety-seven thousand, six hundred forty-nine".