649721 has 4 divisors (see below), whose sum is σ = 658944. Its totient is φ = 640500.

The previous prime is 649717. The next prime is 649739. The reversal of 649721 is 127946.

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 649721 - 2² = 649717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 649721.

It is not an unprimeable number, because it can be changed into a prime (649751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4505 + ... + 4646.

It is an arithmetic number, because the mean of its divisors is an integer number (164736).

2⁶⁴⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

649721 is a deficient number, since it is larger than the sum of its proper divisors (9223).

649721 is an equidigital number, since it uses as much as digits as its factorization.

649721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9222.

The product of its digits is 3024, while the sum is 29.

The square root of 649721 is about 806.0527278038. The cubic root of 649721 is about 86.6115148778.

The spelling of 649721 in words is "six hundred forty-nine thousand, seven hundred twenty-one".