66721560 has 64 divisors (see below), whose sum is σ = 200793600. Its totient is φ = 17736576.

The previous prime is 66721553. The next prime is 66721561. The reversal of 66721560 is 6512766.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66721561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49617 + ... + 50943.

It is an arithmetic number, because the mean of its divisors is an integer number (3137400).

Almost surely, 2^66721560 is an apocalyptic number.

66721560 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66721560 is an abundant number, since it is smaller than the sum of its proper divisors (134072040).

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

66721560 is a wasteful number, since it uses less digits than its factorization.

66721560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1760 (or 1756 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 33.

The square root of 66721560 is about 8168.3266340175. The cubic root of 66721560 is about 405.5913932871.

The spelling of 66721560 in words is "sixty-six million, seven hundred twenty-one thousand, five hundred sixty".