661857900205 has 16 divisors (see below), whose sum is σ = 794713420800. Its totient is φ = 529163819968.

The previous prime is 661857900139. The next prime is 661857900259. The reversal of 661857900205 is 502009758166.

661857900205 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 661857900205 - 2³⁵ = 627498161837 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91249359 + ... + 91256611.

It is an arithmetic number, because the mean of its divisors is an integer number (49669588800).

Almost surely, 2^661857900205 is an apocalyptic number.

It is an amenable number.

661857900205 is a deficient number, since it is larger than the sum of its proper divisors (132855520595).

661857900205 is a wasteful number, since it uses less digits than its factorization.

661857900205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15860.

The product of its (nonzero) digits is 907200, while the sum is 49.

The spelling of 661857900205 in words is "six hundred sixty-one billion, eight hundred fifty-seven million, nine hundred thousand, two hundred five".