661663 has 2 divisors, whose sum is σ = 661664. Its totient is φ = 661662.

The previous prime is 661621. The next prime is 661673. The reversal of 661663 is 366166.

661663 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661663 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330831 + 330832.

It is an arithmetic number, because the mean of its divisors is an integer number (330832).

2⁶⁶¹⁶⁶³ is an apocalyptic number.

661663 is a deficient number, since it is larger than the sum of its proper divisors (1).

661663 is an equidigital number, since it uses as much as digits as its factorization.

661663 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 28.

The square root of 661663 is about 813.4267022910. The cubic root of 661663 is about 87.1389421207.

The spelling of 661663 in words is "six hundred sixty-one thousand, six hundred sixty-three".