647521 has 4 divisors (see below), whose sum is σ = 740032. Its totient is φ = 555012.

The previous prime is 647509. The next prime is 647527. The reversal of 647521 is 125746.

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 an emirpimes, since its reverse is a distinct semiprime: 125746 = 2 ⋅62873.

It is a cyclic number.

It is not a de Polignac number, because 647521 - 2⁵ = 647489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647527) 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, 46245 + ... + 46258.

It is an arithmetic number, because the mean of its divisors is an integer number (185008).

2⁶⁴⁷⁵²¹ is an apocalyptic number.

It is an amenable number.

647521 is a deficient number, since it is larger than the sum of its proper divisors (92511).

647521 is an equidigital number, since it uses as much as digits as its factorization.

647521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92510.

The product of its digits is 1680, while the sum is 25.

The square root of 647521 is about 804.6868956308. The cubic root of 647521 is about 86.5136468161.

The spelling of 647521 in words is "six hundred forty-seven thousand, five hundred twenty-one".