647721 has 12 divisors (see below), whose sum is σ = 948480. Its totient is φ = 425880.

The previous prime is 647719. The next prime is 647723. The reversal of 647721 is 127746.

It is an interprime number because it is at equal distance from previous prime (647719) and next prime (647723).

It is not a de Polignac number, because 647721 - 2¹ = 647719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (647723) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 256 + ... + 1166.

It is an arithmetic number, because the mean of its divisors is an integer number (79040).

2⁶⁴⁷⁷²¹ is an apocalyptic number.

It is an amenable number.

647721 is a deficient number, since it is larger than the sum of its proper divisors (300759).

647721 is a wasteful number, since it uses less digits than its factorization.

647721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 996 (or 993 counting only the distinct ones).

The product of its digits is 2352, while the sum is 27.

The square root of 647721 is about 804.8111579743. The cubic root of 647721 is about 86.5225530643.

The spelling of 647721 in words is "six hundred forty-seven thousand, seven hundred twenty-one".