639699 has 16 divisors (see below), whose sum is σ = 909312. Its totient is φ = 399168.

The previous prime is 639697. The next prime is 639701. The reversal of 639699 is 996936.

639699 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (639697) and next prime (639701).

It is not a de Polignac number, because 639699 - 2¹ = 639697 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 639699.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639697) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4974 + ... + 5100.

It is an arithmetic number, because the mean of its divisors is an integer number (56832).

2⁶³⁹⁶⁹⁹ is an apocalyptic number.

639699 is a gapful number since it is divisible by the number (69) formed by its first and last digit.

639699 is a deficient number, since it is larger than the sum of its proper divisors (269613).

639699 is a wasteful number, since it uses less digits than its factorization.

639699 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226.

The product of its digits is 78732, while the sum is 42.

The square root of 639699 is about 799.8118528754. The cubic root of 639699 is about 86.1638753819.

The spelling of 639699 in words is "six hundred thirty-nine thousand, six hundred ninety-nine".