661217355 has 12 divisors (see below), whose sum is σ = 1146110160. Its totient is φ = 352649232.

The previous prime is 661217327. The next prime is 661217387. The reversal of 661217355 is 553712166.

661217355 is a `hidden beast` number, since 6 + 612 + 1 + 7 + 35 + 5 = 666.

It is not a de Polignac number, because 661217355 - 2¹⁰ = 661216331 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7346815 + ... + 7346904.

It is an arithmetic number, because the mean of its divisors is an integer number (95509180).

Almost surely, 2^661217355 is an apocalyptic number.

661217355 is a deficient number, since it is larger than the sum of its proper divisors (484892805).

661217355 is a wasteful number, since it uses less digits than its factorization.

661217355 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14693730 (or 14693727 counting only the distinct ones).

The product of its digits is 37800, while the sum is 36.

The square root of 661217355 is about 25714.1469817686. The cubic root of 661217355 is about 871.1937437732.

The spelling of 661217355 in words is "six hundred sixty-one million, two hundred seventeen thousand, three hundred fifty-five".