681787 has 2 divisors, whose sum is σ = 681788. Its totient is φ = 681786.

The previous prime is 681781. The next prime is 681809. The reversal of 681787 is 787186.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681787 is a prime.

681787 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (681781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340893 + 340894.

It is an arithmetic number, because the mean of its divisors is an integer number (340894).

2⁶⁸¹⁷⁸⁷ is an apocalyptic number.

681787 is a deficient number, since it is larger than the sum of its proper divisors (1).

681787 is an equidigital number, since it uses as much as digits as its factorization.

681787 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18816, while the sum is 37.

The square root of 681787 is about 825.7039421003. The cubic root of 681787 is about 88.0135567957.

The spelling of 681787 in words is "six hundred eighty-one thousand, seven hundred eighty-seven".