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66978385 = 517787981
BaseRepresentation
bin1111111110000…
…0001001010001
311200000212001221
43333200021101
5114121302020
610351325041
71442210155
oct377401121
9150025057
1066978385
1134897941
121a520781
1310b513a6
148c77065
155d306aa
hex3fe0251

66978385 has 8 divisors (see below), whose sum is σ = 85102056. Its totient is φ = 50430720.

The previous prime is 66978367. The next prime is 66978389. The reversal of 66978385 is 58387966.

66978385 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 23931664 + 43046721 = 4892^2 + 6561^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66978385 - 29 = 66977873 is a prime.

It is a super-2 number, since 2×669783852 = 8972208114416450, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66978389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 393906 + ... + 394075.

It is an arithmetic number, because the mean of its divisors is an integer number (10637757).

Almost surely, 266978385 is an apocalyptic number.

It is an amenable number.

66978385 is a deficient number, since it is larger than the sum of its proper divisors (18123671).

66978385 is a wasteful number, since it uses less digits than its factorization.

66978385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 788003.

The product of its digits is 2177280, while the sum is 52.

The square root of 66978385 is about 8184.0323190955. The cubic root of 66978385 is about 406.1111285497. Note that the first 4 decimals are identical.

The spelling of 66978385 in words is "sixty-six million, nine hundred seventy-eight thousand, three hundred eighty-five".

Divisors: 1 5 17 85 787981 3939905 13395677 66978385