639400849 has 4 divisors (see below), whose sum is σ = 639453760. Its totient is φ = 639347940.

The previous prime is 639400829. The next prime is 639400891. The reversal of 639400849 is 948004936.

639400849 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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 639400849 - 2⁷ = 639400721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639400829) 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, 1564 + ... + 35794.

It is an arithmetic number, because the mean of its divisors is an integer number (159863440).

Almost surely, 2^639400849 is an apocalyptic number.

It is an amenable number.

639400849 is a deficient number, since it is larger than the sum of its proper divisors (52911).

639400849 is a wasteful number, since it uses less digits than its factorization.

639400849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52910.

The product of its (nonzero) digits is 186624, while the sum is 43.

The square root of 639400849 is about 25286.3767471736. The cubic root of 639400849 is about 861.5048687789.

The spelling of 639400849 in words is "six hundred thirty-nine million, four hundred thousand, eight hundred forty-nine".