661555605 has 16 divisors (see below), whose sum is σ = 1058877504. Its totient is φ = 352700160.

The previous prime is 661555603. The next prime is 661555607. The reversal of 661555605 is 506555166.

It is an interprime number because it is at equal distance from previous prime (661555603) and next prime (661555607).

It is not a de Polignac number, because 661555605 - 2¹ = 661555603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661555603) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45645 + ... + 58365.

It is an arithmetic number, because the mean of its divisors is an integer number (66179844).

Almost surely, 2^661555605 is an apocalyptic number.

It is an amenable number.

661555605 is a deficient number, since it is larger than the sum of its proper divisors (397321899).

661555605 is a wasteful number, since it uses less digits than its factorization.

661555605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16196.

The product of its (nonzero) digits is 135000, while the sum is 39.

The square root of 661555605 is about 25720.7232596597. The cubic root of 661555605 is about 871.3422733740.

The spelling of 661555605 in words is "six hundred sixty-one million, five hundred fifty-five thousand, six hundred five".