646638257 has 4 divisors (see below), whose sum is σ = 661676400. Its totient is φ = 631600116.

The previous prime is 646638253. The next prime is 646638263. The reversal of 646638257 is 752836646.

646638257 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 646638257 - 2² = 646638253 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646638253) 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, 7519007 + ... + 7519092.

It is an arithmetic number, because the mean of its divisors is an integer number (165419100).

Almost surely, 2^646638257 is an apocalyptic number.

It is an amenable number.

646638257 is a deficient number, since it is larger than the sum of its proper divisors (15038143).

646638257 is a wasteful number, since it uses less digits than its factorization.

646638257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15038142.

The product of its digits is 1451520, while the sum is 47.

The square root of 646638257 is about 25429.0828973441. The cubic root of 646638257 is about 864.7431524934.

The spelling of 646638257 in words is "six hundred forty-six million, six hundred thirty-eight thousand, two hundred fifty-seven".