66640788 has 18 divisors (see below), whose sum is σ = 168453194. Its totient is φ = 22213584.

The previous prime is 66640787. The next prime is 66640801. The reversal of 66640788 is 88704666.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 61496964 + 5143824 = 7842^2 + 2268^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66640787) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 925531 + ... + 925602.

Almost surely, 2^66640788 is an apocalyptic number.

It is an amenable number.

66640788 is an abundant number, since it is smaller than the sum of its proper divisors (101812406).

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

66640788 is a wasteful number, since it uses less digits than its factorization.

66640788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1851143 (or 1851138 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 45.

The square root of 66640788 is about 8163.3809172426. The cubic root of 66640788 is about 405.4276598219.

The spelling of 66640788 in words is "sixty-six million, six hundred forty thousand, seven hundred eighty-eight".