649681999 has 4 divisors (see below), whose sum is σ = 649899936. Its totient is φ = 649464064.

The previous prime is 649681993. The next prime is 649682009. The reversal of 649681999 is 999186946.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 649681999 - 2¹³ = 649673807 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 (649681993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104434 + ... + 110479.

It is an arithmetic number, because the mean of its divisors is an integer number (162474984).

Almost surely, 2^649681999 is an apocalyptic number.

649681999 is a deficient number, since it is larger than the sum of its proper divisors (217937).

649681999 is a wasteful number, since it uses less digits than its factorization.

649681999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217936.

The product of its digits is 7558272, while the sum is 61.

The square root of 649681999 is about 25488.8602922924. The cubic root of 649681999 is about 866.0978182455.

The spelling of 649681999 in words is "six hundred forty-nine million, six hundred eighty-one thousand, nine hundred ninety-nine".