66721764 has 48 divisors (see below), whose sum is σ = 159941376. Its totient is φ = 21638400.

The previous prime is 66721757. The next prime is 66721769. The reversal of 66721764 is 46712766.

Its product of digits (84672) is a multiple of the sum of its prime factors (756).

It is not an unprimeable number, because it can be changed into a prime (66721769) 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, 158274 + ... + 158694.

It is an arithmetic number, because the mean of its divisors is an integer number (3332112).

Almost surely, 2^66721764 is an apocalyptic number.

It is an amenable number.

66721764 is an abundant number, since it is smaller than the sum of its proper divisors (93219612).

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

66721764 is a wasteful number, since it uses less digits than its factorization.

66721764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 756 (or 754 counting only the distinct ones).

The product of its digits is 84672, while the sum is 39.

The square root of 66721764 is about 8168.3391212657. The cubic root of 66721764 is about 405.5918066495.

The spelling of 66721764 in words is "sixty-six million, seven hundred twenty-one thousand, seven hundred sixty-four".