639946731 has 4 divisors (see below), whose sum is σ = 853262312. Its totient is φ = 426631152.

The previous prime is 639946711. The next prime is 639946859. The reversal of 639946731 is 137649936.

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

It is not a de Polignac number, because 639946731 - 2¹³ = 639938539 is a prime.

It is a super-2 number, since 2×639946731² = 819063637035172722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639946711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106657786 + ... + 106657791.

It is an arithmetic number, because the mean of its divisors is an integer number (213315578).

Almost surely, 2^639946731 is an apocalyptic number.

639946731 is a deficient number, since it is larger than the sum of its proper divisors (213315581).

639946731 is a wasteful number, since it uses less digits than its factorization.

639946731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213315580.

The product of its digits is 734832, while the sum is 48.

The square root of 639946731 is about 25297.1684383846. The cubic root of 639946731 is about 861.7499660616.

The spelling of 639946731 in words is "six hundred thirty-nine million, nine hundred forty-six thousand, seven hundred thirty-one".