661555633 has 8 divisors (see below), whose sum is σ = 670481856. Its totient is φ = 652688400.

The previous prime is 661555619. The next prime is 661555649. The reversal of 661555633 is 336555166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661555633 is a prime.

It is a Duffinian 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 7 ways as a sum of consecutive naturals, for example, 8068 + ... + 37258.

It is an arithmetic number, because the mean of its divisors is an integer number (83810232).

Almost surely, 2^661555633 is an apocalyptic number.

It is an amenable number.

661555633 is a deficient number, since it is larger than the sum of its proper divisors (8926223).

661555633 is a wasteful number, since it uses less digits than its factorization.

661555633 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29495.

The product of its digits is 243000, while the sum is 40.

The square root of 661555633 is about 25720.7238039679. The cubic root of 661555633 is about 871.3422856670.

The spelling of 661555633 in words is "six hundred sixty-one million, five hundred fifty-five thousand, six hundred thirty-three".