647667721 has 8 divisors (see below), whose sum is σ = 676448640. Its totient is φ = 619480368.

The previous prime is 647667707. The next prime is 647667731. The reversal of 647667721 is 127766746.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 647667721 - 2⁵ = 647667689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647667731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 146161 + ... + 150526.

It is an arithmetic number, because the mean of its divisors is an integer number (84556080).

Almost surely, 2^647667721 is an apocalyptic number.

It is an amenable number.

647667721 is a deficient number, since it is larger than the sum of its proper divisors (28780919).

647667721 is a wasteful number, since it uses less digits than its factorization.

647667721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296783.

The product of its digits is 592704, while the sum is 46.

The square root of 647667721 is about 25449.3167098844. The cubic root of 647667721 is about 865.2018066348.

The spelling of 647667721 in words is "six hundred forty-seven million, six hundred sixty-seven thousand, seven hundred twenty-one".