661565097 has 16 divisors (see below), whose sum is σ = 980527680. Its totient is φ = 440849376.

The previous prime is 661565089. The next prime is 661565119. The reversal of 661565097 is 790565166.

It is not a de Polignac number, because 661565097 - 2³ = 661565089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661565297) 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, 84178 + ... + 91700.

It is an arithmetic number, because the mean of its divisors is an integer number (61282980).

Almost surely, 2^661565097 is an apocalyptic number.

It is an amenable number.

661565097 is a deficient number, since it is larger than the sum of its proper divisors (318962583).

661565097 is a wasteful number, since it uses less digits than its factorization.

661565097 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10789 (or 10783 counting only the distinct ones).

The product of its (nonzero) digits is 340200, while the sum is 45.

The square root of 661565097 is about 25720.9077794700. The cubic root of 661565097 is about 871.3464406938.

It can be divided in two parts, 66156 and 5097, that added together give a triangular number (71253 = T₃₇₇).

The spelling of 661565097 in words is "six hundred sixty-one million, five hundred sixty-five thousand, ninety-seven".