649721438809 has 9 divisors (see below), whose sum is σ = 651769594749. Its totient is φ = 647679706560.

The previous prime is 649721438803. The next prime is 649721438837. The reversal of 649721438809 is 908834127946.

The square root of 649721438809 is 806053.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 19012273225 + 630709165584 = 137885^2 + 794172^2 .

It is not a de Polignac number, because 649721438809 - 2⁵ = 649721438777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (649721438803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 300656689 + ... + 300658849.

It is an arithmetic number, because the mean of its divisors is an integer number (72418843861).

Almost surely, 2^649721438809 is an apocalyptic number.

649721438809 is the 806053-rd square number.

649721438809 is the 403027-th centered octagonal number.

It is an amenable number.

649721438809 is a deficient number, since it is larger than the sum of its proper divisors (2048155940).

649721438809 is an frugal number, since it uses more digits than its factorization.

649721438809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5068 (or 2534 counting only the distinct ones).

The product of its (nonzero) digits is 20901888, while the sum is 61.

The spelling of 649721438809 in words is "six hundred forty-nine billion, seven hundred twenty-one million, four hundred thirty-eight thousand, eight hundred nine".