687739 has 4 divisors (see below), whose sum is σ = 740656. Its totient is φ = 634824.

The previous prime is 687737. The next prime is 687749. The reversal of 687739 is 937786.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 937786 = 2 ⋅468893.

It is a cyclic number.

It is not a de Polignac number, because 687739 - 2¹ = 687737 is a prime.

It is a Duffinian number.

687739 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (687737) 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, 26439 + ... + 26464.

It is an arithmetic number, because the mean of its divisors is an integer number (185164).

2⁶⁸⁷⁷³⁹ is an apocalyptic number.

687739 is a deficient number, since it is larger than the sum of its proper divisors (52917).

687739 is a wasteful number, since it uses less digits than its factorization.

687739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52916.

The product of its digits is 63504, while the sum is 40.

The square root of 687739 is about 829.3003074882. The cubic root of 687739 is about 88.2689345104.

Subtracting 687739 from its reverse (937786), we obtain a cube (250047 = 63³).

The spelling of 687739 in words is "six hundred eighty-seven thousand, seven hundred thirty-nine".