66561600 has 252 divisors, whose sum is σ = 254928624. Its totient is φ = 15160320.

The previous prime is 66561571. The next prime is 66561611. The reversal of 66561600 is 616566.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 235059 + ... + 235341.

Almost surely, 2^66561600 is an apocalyptic number.

66561600 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66561600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (127464312).

66561600 is an abundant number, since it is smaller than the sum of its proper divisors (188367024).

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

66561600 is a wasteful number, since it uses less digits than its factorization.

66561600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322 (or 300 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 66561600 is about 8158.5292792267. The cubic root of 66561600 is about 405.2670088078.

It can be divided in two parts, 66561 and 600, that added together give a triangular number (67161 = T₃₆₆).

The spelling of 66561600 in words is "sixty-six million, five hundred sixty-one thousand, six hundred".