66681340020 has 60 divisors (see below), whose sum is σ = 209181838404. Its totient is φ = 17781690240.

The previous prime is 66681339961. The next prime is 66681340021. The reversal of 66681340020 is 2004318666.

It can be written as a sum of positive squares in 2 ways, for example, as 7571088144 + 59110251876 = 87012^2 + 243126^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a super-2 number, since 2×66681340020² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66681340021) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 20579041 + ... + 20582280.

Almost surely, 2^66681340020 is an apocalyptic number.

66681340020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66681340020 is an abundant number, since it is smaller than the sum of its proper divisors (142500498384).

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

66681340020 is a wasteful number, since it uses less digits than its factorization.

66681340020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41161342 (or 41161331 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

Adding to 66681340020 its reverse (2004318666), we get a palindrome (68685658686).

The spelling of 66681340020 in words is "sixty-six billion, six hundred eighty-one million, three hundred forty thousand, twenty".