646738123 has 4 divisors (see below), whose sum is σ = 684781560. Its totient is φ = 608694688.

The previous prime is 646738121. The next prime is 646738129. The reversal of 646738123 is 321837646.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 646738123 - 2¹ = 646738121 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646738121) 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, 19021693 + ... + 19021726.

It is an arithmetic number, because the mean of its divisors is an integer number (171195390).

Almost surely, 2^646738123 is an apocalyptic number.

646738123 is a deficient number, since it is larger than the sum of its proper divisors (38043437).

646738123 is a wasteful number, since it uses less digits than its factorization.

646738123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38043436.

The product of its digits is 145152, while the sum is 40.

The square root of 646738123 is about 25431.0464393426. The cubic root of 646738123 is about 864.7876668173.

The spelling of 646738123 in words is "six hundred forty-six million, seven hundred thirty-eight thousand, one hundred twenty-three".