661817856525 has 48 divisors (see below), whose sum is σ = 1250705140224. Its totient is φ = 302500658880.

The previous prime is 661817856517. The next prime is 661817856527. The reversal of 661817856525 is 525658718166.

It is not a de Polignac number, because 661817856525 - 2³ = 661817856517 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661817856527) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3608082 + ... + 3787068.

It is an arithmetic number, because the mean of its divisors is an integer number (26056357088).

Almost surely, 2^661817856525 is an apocalyptic number.

It is an amenable number.

661817856525 is a deficient number, since it is larger than the sum of its proper divisors (588887283699).

661817856525 is a wasteful number, since it uses less digits than its factorization.

661817856525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 186050 (or 186045 counting only the distinct ones).

The product of its digits is 24192000, while the sum is 60.

The spelling of 661817856525 in words is "six hundred sixty-one billion, eight hundred seventeen million, eight hundred fifty-six thousand, five hundred twenty-five".