646668751 has 4 divisors (see below), whose sum is σ = 646980400. Its totient is φ = 646357104.

The previous prime is 646668707. The next prime is 646668809. The reversal of 646668751 is 157866646.

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 646668751 - 2⁷ = 646668623 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 646668695 and 646668704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646666751) 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, 152691 + ... + 156868.

It is an arithmetic number, because the mean of its divisors is an integer number (161745100).

Almost surely, 2^646668751 is an apocalyptic number.

646668751 is a deficient number, since it is larger than the sum of its proper divisors (311649).

646668751 is a wasteful number, since it uses less digits than its factorization.

646668751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311648.

The product of its digits is 1451520, while the sum is 49.

The square root of 646668751 is about 25429.6824793390. The cubic root of 646668751 is about 864.7567453912.

The spelling of 646668751 in words is "six hundred forty-six million, six hundred sixty-eight thousand, seven hundred fifty-one".