639686993 has 4 divisors (see below), whose sum is σ = 697840368. Its totient is φ = 581533620.

The previous prime is 639686951. The next prime is 639687001. The reversal of 639686993 is 399686936.

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 639686993 - 2¹⁴ = 639670609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639686933) 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, 29076671 + ... + 29076692.

It is an arithmetic number, because the mean of its divisors is an integer number (174460092).

Almost surely, 2^639686993 is an apocalyptic number.

It is an amenable number.

639686993 is a deficient number, since it is larger than the sum of its proper divisors (58153375).

639686993 is a wasteful number, since it uses less digits than its factorization.

639686993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58153374.

The product of its digits is 11337408, while the sum is 59.

The square root of 639686993 is about 25292.0341807455. The cubic root of 639686993 is about 861.6333628659.

The spelling of 639686993 in words is "six hundred thirty-nine million, six hundred eighty-six thousand, nine hundred ninety-three".