661781600 has 36 divisors (see below), whose sum is σ = 1615576284. Its totient is φ = 264712320.

The previous prime is 661781597. The next prime is 661781611. The reversal of 661781600 is 6187166.

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 412814 + ... + 414413.

It is an arithmetic number, because the mean of its divisors is an integer number (44877119).

Almost surely, 2^661781600 is an apocalyptic number.

It is an amenable number.

661781600 is an abundant number, since it is smaller than the sum of its proper divisors (953794684).

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

661781600 is a wasteful number, since it uses less digits than its factorization.

661781600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 827247 (or 827234 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 661781600 is about 25725.1161319050. The cubic root of 661781600 is about 871.4414822571.

The spelling of 661781600 in words is "six hundred sixty-one million, seven hundred eighty-one thousand, six hundred".