661679 has 2 divisors, whose sum is σ = 661680. Its totient is φ = 661678.

The previous prime is 661673. The next prime is 661697. The reversal of 661679 is 976166.

It is a happy number.

661679 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

Together with next prime (661697) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661679 - 2⁴ = 661663 is a prime.

It is a Chen prime.

It is a plaindrome in base 12.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661673) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330839 + 330840.

It is an arithmetic number, because the mean of its divisors is an integer number (330840).

2⁶⁶¹⁶⁷⁹ is an apocalyptic number.

661679 is a deficient number, since it is larger than the sum of its proper divisors (1).

661679 is an equidigital number, since it uses as much as digits as its factorization.

661679 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13608, while the sum is 35.

The square root of 661679 is about 813.4365371681. The cubic root of 661679 is about 87.1396444983.

The spelling of 661679 in words is "six hundred sixty-one thousand, six hundred seventy-nine".