661516605 has 16 divisors (see below), whose sum is σ = 1176029760. Its totient is φ = 352808784.

The previous prime is 661516579. The next prime is 661516621. The reversal of 661516605 is 506615166.

It is not a de Polignac number, because 661516605 - 2¹⁷ = 661385533 is a prime.

661516605 is a modest number, since divided by 16605 gives 6615 as remainder.

It is a self number, because there is not a number n which added to its sum of digits gives 661516605.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2449927 + ... + 2450196.

It is an arithmetic number, because the mean of its divisors is an integer number (73501860).

Almost surely, 2^661516605 is an apocalyptic number.

It is an amenable number.

661516605 is a deficient number, since it is larger than the sum of its proper divisors (514513155).

661516605 is a wasteful number, since it uses less digits than its factorization.

661516605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4900137 (or 4900131 counting only the distinct ones).

The product of its (nonzero) digits is 32400, while the sum is 36.

The square root of 661516605 is about 25719.9651049530. The cubic root of 661516605 is about 871.3251505924.

It can be divided in two parts, 6615 and 16605, that added together give a triangular number (23220 = T₂₁₅).

The spelling of 661516605 in words is "six hundred sixty-one million, five hundred sixteen thousand, six hundred five".