639987993 has 8 divisors (see below), whose sum is σ = 948130400. Its totient is φ = 426658644.

The previous prime is 639987991. The next prime is 639988031. The reversal of 639987993 is 399789936.

It is not a de Polignac number, because 639987993 - 2¹ = 639987991 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639987993.

It is not an unprimeable number, because it can be changed into a prime (639987991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11851603 + ... + 11851656.

It is an arithmetic number, because the mean of its divisors is an integer number (118516300).

Almost surely, 2^639987993 is an apocalyptic number.

It is an amenable number.

639987993 is a deficient number, since it is larger than the sum of its proper divisors (308142407).

639987993 is a wasteful number, since it uses less digits than its factorization.

639987993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23703268 (or 23703262 counting only the distinct ones).

The product of its digits is 19840464, while the sum is 63.

The square root of 639987993 is about 25297.9839710598. The cubic root of 639987993 is about 861.7684867504.

The spelling of 639987993 in words is "six hundred thirty-nine million, nine hundred eighty-seven thousand, nine hundred ninety-three".