646043591 has 4 divisors (see below), whose sum is σ = 647033592. Its totient is φ = 645053592.

The previous prime is 646043549. The next prime is 646043603. The reversal of 646043591 is 195340646.

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 646043591 - 2²² = 641849287 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646043891) 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, 494021 + ... + 495326.

It is an arithmetic number, because the mean of its divisors is an integer number (161758398).

Almost surely, 2^646043591 is an apocalyptic number.

646043591 is a deficient number, since it is larger than the sum of its proper divisors (990001).

646043591 is an equidigital number, since it uses as much as digits as its factorization.

646043591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 990000.

The product of its (nonzero) digits is 77760, while the sum is 38.

The square root of 646043591 is about 25417.3875722900. The cubic root of 646043591 is about 864.4779908100.

The spelling of 646043591 in words is "six hundred forty-six million, forty-three thousand, five hundred ninety-one".