639749 has 8 divisors (see below), whose sum is σ = 734880. Its totient is φ = 550800.

The previous prime is 639739. The next prime is 639757. The reversal of 639749 is 947936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639749 - 2⁸ = 639493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639719) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1322 + ... + 1739.

It is an arithmetic number, because the mean of its divisors is an integer number (91860).

2⁶³⁹⁷⁴⁹ is an apocalyptic number.

It is an amenable number.

639749 is a deficient number, since it is larger than the sum of its proper divisors (95131).

639749 is a wasteful number, since it uses less digits than its factorization.

639749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3091.

The product of its digits is 40824, while the sum is 38.

The square root of 639749 is about 799.8431096159. The cubic root of 639749 is about 86.1661202301.

It can be divided in two parts, 6397 and 49, that added together give a palindrome (6446).

The spelling of 639749 in words is "six hundred thirty-nine thousand, seven hundred forty-nine".