661616 has 10 divisors (see below), whose sum is σ = 1281912. Its totient is φ = 330800.

The previous prime is 661613. The next prime is 661621. The reversal of 661616 is 616166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20660 + ... + 20691.

2⁶⁶¹⁶¹⁶ is an apocalyptic number.

It is an amenable number.

661616 is a deficient number, since it is larger than the sum of its proper divisors (620296).

661616 is a wasteful number, since it uses less digits than its factorization.

661616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41359 (or 41353 counting only the distinct ones).

The product of its digits is 1296, while the sum is 26.

The square root of 661616 is about 813.3978116518. The cubic root of 661616 is about 87.1368788210.

The spelling of 661616 in words is "six hundred sixty-one thousand, six hundred sixteen".