661557805170 has 32 divisors (see below), whose sum is σ = 1681135129728. Its totient is φ = 166038037248.

The previous prime is 661557805157. The next prime is 661557805177. The reversal of 661557805170 is 71508755166.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is not an unprimeable number, because it can be changed into a prime (661557805177) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 648585574 + ... + 648586593.

It is an arithmetic number, because the mean of its divisors is an integer number (52535472804).

Almost surely, 2^661557805170 is an apocalyptic number.

661557805170 is an abundant number, since it is smaller than the sum of its proper divisors (1019577324558).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661557805170 is a wasteful number, since it uses less digits than its factorization.

661557805170 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1297172194.

The product of its (nonzero) digits is 1764000, while the sum is 51.

The spelling of 661557805170 in words is "six hundred sixty-one billion, five hundred fifty-seven million, eight hundred five thousand, one hundred seventy".