643799977 has 4 divisors (see below), whose sum is σ = 644117760. Its totient is φ = 643482196.

The previous prime is 643799941. The next prime is 643799983. The reversal of 643799977 is 779997346.

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 643799977 - 2²³ = 635411369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643799927) 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, 155833 + ... + 159910.

It is an arithmetic number, because the mean of its divisors is an integer number (161029440).

Almost surely, 2^643799977 is an apocalyptic number.

It is an amenable number.

643799977 is a deficient number, since it is larger than the sum of its proper divisors (317783).

643799977 is a wasteful number, since it uses less digits than its factorization.

643799977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317782.

The product of its digits is 18003384, while the sum is 61.

The square root of 643799977 is about 25373.2137696430. The cubic root of 643799977 is about 863.4760952957.

The spelling of 643799977 in words is "six hundred forty-three million, seven hundred ninety-nine thousand, nine hundred seventy-seven".