647657993 has 8 divisors (see below), whose sum is σ = 685978920. Its totient is φ = 609361920.

The previous prime is 647657987. The next prime is 647658007. The reversal of 647657993 is 399756746.

It can be written as a sum of positive squares in 4 ways, for example, as 150724729 + 496933264 = 12277^2 + 22292^2 .

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 647657993 - 2⁴ = 647657977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (647657903) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 91253 + ... + 98093.

It is an arithmetic number, because the mean of its divisors is an integer number (85747365).

Almost surely, 2^647657993 is an apocalyptic number.

It is an amenable number.

647657993 is a deficient number, since it is larger than the sum of its proper divisors (38320927).

647657993 is a wasteful number, since it uses less digits than its factorization.

647657993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12427.

The product of its digits is 8573040, while the sum is 56.

The square root of 647657993 is about 25449.1255841925. The cubic root of 647657993 is about 865.1974748224.

The spelling of 647657993 in words is "six hundred forty-seven million, six hundred fifty-seven thousand, nine hundred ninety-three".